2.0 Changelog

2.0.23

Released: November 2, 2023

orm

• [orm] [usecase]

  Implemented the Session.bulk_insert_mappings.render_nulls parameter for new style bulk ORM inserts, allowing render_nulls=True as an execution option. This allows for bulk ORM inserts with a mixture of None values in the parameter dictionaries to use a single batch of rows for a given set of dicationary keys, rather than breaking up into batches that omit the NULL columns from each INSERT.

  See also

  Sending NULL values in ORM bulk INSERT statements

  References: #10575

• [orm] [bug]

  Fixed issue where the __allow_unmapped__ directive failed to allow for legacy Column / deferred() mappings that nonetheless had annotations such as Any or a specific type without Mapped[] as their type, without errors related to locating the attribute name.

  References: #10516

• [orm] [bug]

  Fixed caching bug where using the with_expression() construct in conjunction with loader options selectinload(), lazyload() would fail to substitute bound parameter values correctly on subsequent caching runs.

  References: #10570

• [orm] [bug]

  Fixed bug in ORM annotated declarative where using a ClassVar that nonetheless referred in some way to an ORM mapped class name would fail to be interpreted as a ClassVar that’s not mapped.

  References: #10472

sql

• [sql] [usecase]

  Implemented “literal value processing” for the Interval datatype for both the PostgreSQL and Oracle dialects, allowing literal rendering of interval values. Pull request courtesy Indivar Mishra.

  References: #9737

• [sql] [bug]

  Fixed issue where using the same bound parameter more than once with literal_execute=True in some combinations with other literal rendering parameters would cause the wrong values to render due to an iteration issue.

  This change is also backported to: 1.4.50

  References: #10142

• [sql] [bug]

  Added compiler-level None/NULL handling for the “literal processors” of all datatypes that include literal processing, that is, where a value is rendered inline within a SQL statement rather than as a bound parameter, for all those types that do not feature explicit “null value” handling. Previously this behavior was undefined and inconsistent.

  References: #10535

• [sql]

  Removed unused placeholder method TypeEngine.compare_against_backend() This method was used by very old versions of Alembic. See https://github.com/sqlalchemy/alembic/issues/1293 for details.

asyncio

• [asyncio] [bug]

  Fixed bug with method AsyncSession.close_all() that was not working correctly. Also added function close_all_sessions() that’s the equivalent of close_all_sessions(). Pull request courtesy of Bryan不可思议.

  References: #10421

postgresql

• [postgresql] [bug]

  Fixed 2.0 regression caused by #7744 where chains of expressions involving PostgreSQL JSON operators combined with other operators such as string concatenation would lose correct parenthesization, due to an implementation detail specific to the PostgreSQL dialect.

  References: #10479

• [postgresql] [bug]

  Fixed SQL handling for “insertmanyvalues” when using the BIT datatype with the asyncpg backend. The BIT on asyncpg apparently requires the use of an asyncpg-specific BitString type which is currently exposed when using this DBAPI, making it incompatible with other PostgreSQL DBAPIs that all work with plain bitstrings here. A future fix in version 2.1 will normalize this datatype across all PG backends. Pull request courtesy Sören Oldag.

  References: #10532

mysql

• [mysql] [bug]

  Repaired a new incompatibility in the MySQL “pre-ping” routine where the False argument passed to connection.ping(), which is intended to disable an unwanted “automatic reconnect” feature, is being deprecated in MySQL drivers and backends, and is producing warnings for some versions of MySQL’s native client drivers. It’s removed for mysqlclient, whereas for PyMySQL and drivers based on PyMySQL, the parameter will be deprecated and removed at some point, so API introspection is used to future proof against these various stages of removal.

  This change is also backported to: 1.4.50

  References: #10492

mariadb

• [mariadb] [bug]

  Adjusted the MySQL / MariaDB dialects to default a generated column to NULL when using MariaDB, if Column.nullable was not specified with an explicit True or False value, as MariaDB does not support the “NOT NULL” phrase with a generated column. Pull request courtesy Indivar.

  References: #10056

• [mariadb] [bug] [regression]

  Established a workaround for what seems to be an intrinsic issue across MySQL/MariaDB drivers where a RETURNING result for DELETE DML which returns no rows using SQLAlchemy’s “empty IN” criteria fails to provide a cursor.description, which then yields result that returns no rows, leading to regressions for the ORM that in the 2.0 series uses RETURNING for bulk DELETE statements for the “synchronize session” feature. To resolve, when the specific case of “no description when RETURNING was given” is detected, an “empty result” with a correct cursor description is generated and used in place of the non-working cursor.

  References: #10505

mssql

• [mssql] [usecase]

  Added support for the aioodbc driver implemented for SQL Server, which builds on top of the pyodbc and general aio* dialect architecture.

  See also

  aioodbc - in the SQL Server dialect documentation.

  References: #6521

• [mssql] [bug] [reflection]

  Fixed issue where identity column reflection would fail for a bigint column with a large identity start value (more than 18 digits).

  This change is also backported to: 1.4.50

  References: #10504

oracle

• [oracle] [bug]

  Fixed issue in Interval datatype where the Oracle implementation was not being used for DDL generation, leading to the day_precision and second_precision parameters to be ignored, despite being supported by this dialect. Pull request courtesy Indivar.

  References: #10509

• [oracle] [bug]

  Fixed issue where the cx_Oracle dialect claimed to support a lower cx_Oracle version (7.x) than was actually supported in practice within the 2.0 series of SQLAlchemy. The dialect imports symbols that are only in cx_Oracle 8 or higher, so runtime dialect checks as well as setup.cfg requirements have been updated to reflect this compatibility.

  References: #10470

2.0.22

Released: October 12, 2023

orm

• [orm] [usecase]

  Added method Session.get_one() that behaves like Session.get() but raises an exception instead of returning None if no instance was found with the provided primary key. Pull request courtesy of Carlos Sousa.

  References: #10202

• [orm] [usecase]

  Added an option to permanently close sessions. Set to False the new parameter Session.close_resets_only will prevent a Session from performing any other operation after Session.close() has been called.

  Added new method Session.reset() that will reset a Session to its initial state. This is an alias of Session.close(), unless Session.close_resets_only is set to False.

  References: #7787

• [orm] [bug]

  Fixed a wide range of mapped_column() parameters that were not being transferred when using the mapped_column() object inside of a pep-593 Annotated object, including mapped_column.sort_order, mapped_column.deferred, mapped_column.autoincrement, mapped_column.system, mapped_column.info etc.

  Additionally, it remains not supported to have dataclass arguments, such as mapped_column.kw_only, mapped_column.default_factory etc. indicated within the mapped_column() received by Annotated, as this is not supported with pep-681 Dataclass Transforms. A warning is now emitted when these parameters are used within Annotated in this way (and they continue to be ignored).

  References: #10046, #10369

• [orm] [bug]

  Fixed issue where calling Result.unique() with a new-style select() query in the ORM, where one or more columns yields values that are of “unknown hashability”, typically when using JSON functions like func.json_build_object() without providing a type, would fail internally when the returned values were not actually hashable. The behavior is repaired to test the objects as they are received for hashability in this case, raising an informative error message if not. Note that for values of “known unhashability”, such as when the JSON or ARRAY types are used directly, an informative error message was already raised.

  The “hashabiltiy testing” fix here is applied to legacy Query as well, however in the legacy case, Result.unique() is used for nearly all queries, so no new warning is emitted here; the legacy behavior of falling back to using id() in this case is maintained, with the improvement that an unknown type that turns out to be hashable will now be uniqufied, whereas previously it would not.

  References: #10459

• [orm] [bug]

  Fixed regression in recently revised “insertmanyvalues” feature (likely issue #9618) where the ORM would inadvertently attempt to interpret a non-RETURNING result as one with RETURNING, in the case where the implicit_returning=False parameter were applied to the mapped Table, indicating that “insertmanyvalues” cannot be used if the primary key values are not provided.

  References: #10453

• [orm] [bug]

  Fixed bug where ORM with_loader_criteria() would not apply itself to a Select.join() where the ON clause were given as a plain SQL comparison, rather than as a relationship target or similar.

  References: #10365

• [orm] [bug]

  Fixed issue where Mapped symbols like WriteOnlyMapped and DynamicMapped could not be correctly resolved when referenced as an element of a sub-module in the given annotation, assuming string-based or “future annotations” style annotations.

  References: #10412

• [orm] [bug]

  Fixed issue with __allow_unmapped__ declarative option where types that were declared using collection types such as list[SomeClass] vs. the typing construct List[SomeClass] would fail to be recognized correctly. Pull request courtesy Pascal Corpet.

  References: #10385

engine

• [engine] [bug]

  Fixed issue within some dialects where the dialect could incorrectly return an empty result set for an INSERT statement that does not actually return rows at all, due to artfacts from pre- or post-fetching the primary key of the row or rows still being present. Affected dialects included asyncpg, all mssql dialects.

• [engine] [bug]

  Fixed issue where under some garbage collection / exception scenarios the connection pool’s cleanup routine would raise an error due to an unexpected set of state, which can be reproduced under specific conditions.

  References: #10414

sql

• [sql] [bug]

  Fixed issue where referring to a FROM entry in the SET clause of an UPDATE statement would not include it in the FROM clause of the UPDATE statement, if that entry were nowhere else in the statement; this occurs currently for CTEs that were added using Update.add_cte() to provide the desired CTE at the top of the statement.

  References: #10408

• [sql] [bug]

  Fixed 2.0 regression where the DDL construct would no longer __repr__() due to the removed on attribute not being accommodated. Pull request courtesy Iuri de Silvio.

  References: #10443

typing

• [typing] [bug]

  Fixed typing issue where the argument list passed to Values was too-restrictively tied to List rather than Sequence. Pull request courtesy Iuri de Silvio.

  References: #10451

• [typing] [bug]

  Updates to the codebase to support Mypy 1.6.0.

asyncio

• [asyncio] [bug]

  Fixed the AsyncSession.get.execution_options parameter which was not being propagated to the underlying Session and was instead being ignored.

mariadb

• [mariadb] [bug]

  Modified the mariadb-connector driver to pre-load the cursor.rowcount value for all queries, to suit tools such as Pandas that hardcode to calling Result.rowcount in this way. SQLAlchemy normally pre-loads cursor.rowcount only for UPDATE/DELETE statements and otherwise passes through to the DBAPI where it can return -1 if no value is available. However, mariadb-connector does not support invoking cursor.rowcount after the cursor itself is closed, raising an error instead. Generic test support has been added to ensure all backends support the allowing Result.rowcount to succceed (that is, returning an integer value with -1 for “not available”) after the result is closed.

  References: #10396

• [mariadb] [bug]

  Additional fixes for the mariadb-connector dialect to support UUID data values in the result in INSERT..RETURNING statements.

mssql

• [mssql] [bug]

  Fixed bug where the rule that prevents ORDER BY from emitting within subqueries on SQL Server was not being disabled in the case where the select.fetch() method were used to limit rows in conjunction with WITH TIES or PERCENT, preventing valid subqueries with TOP / ORDER BY from being used.

  References: #10458

2.0.21

Released: September 18, 2023

orm

• [orm] [bug]

  Adjusted the ORM’s interpretation of the “target” entity used within Update and Delete to not interfere with the target “from” object passed to the statement, such as when passing an ORM-mapped aliased construct that should be maintained within a phrase like “UPDATE FROM”. Cases like ORM session synchonize using “SELECT” statements such as with MySQL/ MariaDB will still have issues with UPDATE/DELETE of this form so it’s best to disable synchonize_session when using DML statements of this type.

  References: #10279

• [orm] [bug]

  Added new capability to the selectin_polymorphic() loader option which allows other loader options to be bundled as siblings, referring to one of its subclasses, within the sub-options of parent loader option. Previously, this pattern was only supported if the selectin_polymorphic() were at the top level of the options for the query. See new documentation section for example.

  As part of this change, improved the behavior of the Load.selectin_polymorphic() method / loader strategy so that the subclass load does not load most already-loaded columns from the parent table, when the option is used against a class that is already being relationship-loaded. Previously, the logic to load only the subclass columns worked only for a top level class load.

  See also

  Applying loader options when selectin_polymorphic is itself a sub-option

  References: #10348

engine

• [engine] [bug]

  Fixed a series of reflection issues affecting the PostgreSQL, MySQL/MariaDB, and SQLite dialects when reflecting foreign key constraints where the target column contained parenthesis in one or both of the table name or column name.

  References: #10275

sql

• [sql] [usecase]

  Adjusted the Enum datatype to accept an argument of None for the Enum.length parameter, resulting in a VARCHAR or other textual type with no length in the resulting DDL. This allows for new elements of any length to be added to the type after it exists in the schema. Pull request courtesy Eugene Toder.

  References: #10269

• [sql] [usecase]

  Added new generic SQL function aggregate_strings, which accepts a SQL expression and a decimeter, concatenating strings on multiple rows into a single aggregate value. The function is compiled on a per-backend basis, into functions such as group_concat(), string_agg(), or LISTAGG(). Pull request courtesy Joshua Morris.

  References: #9873

• [sql] [bug]

  Adjusted the operator precedence for the string concatenation operator to be equal to that of string matching operators, such as ColumnElement.like(), ColumnElement.regexp_match(), ColumnElement.match(), etc., as well as plain == which has the same precedence as string comparison operators, so that parenthesis will be applied to a string concatenation expression that follows a string match operator. This provides for backends such as PostgreSQL where the “regexp match” operator is apparently of higher precedence than the string concatenation operator.

  References: #9610

• [sql] [bug]

  Qualified the use of hashlib.md5() within the DDL compiler, which is used to generate deterministic four-character suffixes for long index and constraint names in DDL statements, to include the Python 3.9+ usedforsecurity=False parameter so that Python interpreters built for restricted environments such as FIPS do not consider this call to be related to security concerns.

  References: #10342

• [sql] [bug]

  The Values construct will now automatically create a proxy (i.e. a copy) of a column if the column were already associated with an existing FROM clause. This allows that an expression like values_obj.c.colname will produce the correct FROM clause even in the case that colname was passed as a column that was already used with a previous Values or other table construct. Originally this was considered to be a candidate for an error condition, however it’s likely this pattern is already in widespread use so it’s now added to support.

  References: #10280

schema

• [schema] [bug]

  Modified the rendering of the Oracle only Identity.order parameter that’s part of both Sequence and Identity to only take place for the Oracle backend, and not other backends such as that of PostgreSQL. A future release will rename the Identity.order, Sequence.order and Identity.on_null parameters to Oracle-specific names, deprecating the old names, these parameters only apply to Oracle.

  This change is also backported to: 1.4.50

  References: #10207

typing

• [typing] [usecase]

  Made the contained type for Mapped covariant; this is to allow greater flexibility for end-user typing scenarios, such as the use of protocols to represent particular mapped class structures that are passed to other functions. As part of this change, the contained type was also made covariant for dependent and related types such as SQLORMOperations, WriteOnlyMapped, and SQLColumnExpression. Pull request courtesy Roméo Després.

  References: #10288

• [typing] [bug]

  Fixed regression introduced in 2.0.20 via #9600 fix which attempted to add more formal typing to MetaData.naming_convention. This change prevented basic naming convention dictionaries from passing typing and has been adjusted so that a plain dictionary of strings for keys as well as dictionaries that use constraint types as keys or a mix of both, are again accepted.

  As part of this change, lesser used forms of the naming convention dictionary are also typed, including that it currently allows for Constraint type objects as keys as well.

  References: #10264, #9284

• [typing] [bug]

  Fixed the type annotation for __class_getitem__() as applied to the Visitable class at the base of expression constructs to accept Any for a key, rather than str, which helps with some IDEs such as PyCharm when attempting to write typing annotations for SQL constructs which include generic selectors. Pull request courtesy Jordan Macdonald.

  References: #9878

• [typing] [bug]

  Repaired the core “SQL element” class SQLCoreOperations to support the __hash__() method from a typing perspective, as objects like Column and ORM InstrumentedAttribute are hashable and are used as dictionary keys in the public API for the Update and Insert constructs. Previously, type checkers were not aware the root SQL element was hashable.

  References: #10353

• [typing] [bug]

  Fixed typing issue with Existing.select_from() that prevented its use with ORM classes.

  References: #10337

• [typing] [bug]

  Update type annotations for ORM loading options, restricting them to accept only “*” instead of any string for string arguments. Pull request courtesy Janek Nouvertné.

  References: #10131

postgresql

• [postgresql] [bug]

  Fixed regression which appeared in 2.0 due to #8491 where the revised “ping” used for PostgreSQL dialects when the create_engine.pool_pre_ping parameter is in use would interfere with the use of asyncpg with PGBouncer “transaction” mode, as the multiple PostgreSQL commands emitted by asnycpg could be broken out among multiple connections leading to errors, due to the lack of any transaction around this newly revised “ping”. The ping is now invoked within a transaction, in the same way that is implicit with all other backends that are based on the pep-249 DBAPI; this guarantees that the series of PG commands sent by asyncpg for this command are invoked on the same backend connection without it jumping to a different connection mid-command. The transaction is not used if the asyncpg dialect is used in “AUTOCOMMIT” mode, which remains incompatible with pgbouncer transaction mode.

  References: #10226

misc

• [bug] [setup]

  Fixed very old issue where the full extent of SQLAlchemy modules, including sqlalchemy.testing.fixtures, could not be imported outside of a pytest run. This suits inspection utilities such as pkgutil that attempt to import all installed modules in all packages.

  References: #10321

2.0.20

Released: August 15, 2023

orm

• [orm] [usecase]

  Implemented the “RETURNING ‘*’” use case for ORM enabled DML statements. This will render in as many cases as possible and return the unfiltered result set, however is not supported for multi-parameter “ORM bulk INSERT” statements that have specific column rendering requirements.

  References: #10192

• [orm] [bug]

  Fixed fundamental issue which prevented some forms of ORM “annotations” from taking place for subqueries which made use of Select.join() against a relationship target. These annotations are used whenever a subquery is used in special situations such as within PropComparator.and_() and other ORM-specific scenarios.

  This change is also backported to: 1.4.50

  References: #10223

• [orm] [bug]

  Fixed issue where the ORM’s generation of a SELECT from a joined inheritance model with same-named columns in superclass and subclass would somehow not send the correct list of column names to the CTE construct, when the RECURSIVE column list were generated.

  References: #10169

• [orm] [bug]

  Fixed fairly major issue where execution options passed to Session.execute(), as well as execution options local to the ORM executed statement itself, would not be propagated along to eager loaders such as that of selectinload(), immediateload(), and sqlalchemy.orm.subqueryload(), making it impossible to do things such as disabling the cache for a single statement or using schema_translate_map for a single statement, as well as the use of user-custom execution options. A change has been made where all user-facing execution options present for Session.execute() will be propagated along to additional loaders.

  As part of this change, the warning for “excessively deep” eager loaders leading to caching being disabled can be silenced on a per-statement basis by sending execution_options={"compiled_cache": None} to Session.execute(), which will disable caching for the full series of statements within that scope.

  References: #10231

• [orm] [bug]

  Fixed issue where internal cloning used by the ORM for expressions like Comparator.any() to produce correlated EXISTS constructs would interfere with the “cartesian product warning” feature of the SQL compiler, leading the SQL compiler to warn when all elements of the statement were correctly joined.

  References: #10124

• [orm] [bug]

  Fixed issue where the lazy="immediateload" loader strategy would place an internal loading token into the ORM mapped attribute under circumstances where the load should not occur, such as in a recursive self-referential load. As part of this change, the lazy="immediateload" strategy now honors the relationship.join_depth parameter for self-referential eager loads in the same way as that of other eager loaders, where leaving it unset or set at zero will lead to a self-referential immediateload not occurring, setting it to a value of one or greater will immediateload up until that given depth.

  References: #10139

• [orm] [bug]

  Fixed issue where dictionary-based collections such as attribute_keyed_dict() did not fully pickle/unpickle correctly, leading to issues when attempting to mutate such a collection after unpickling.

  References: #10175

• [orm] [bug]

  Fixed issue where chaining load_only() or other wildcard use of defer() from another eager loader using a aliased() against a joined inheritance subclass would fail to take effect for columns local to the superclass.

  References: #10125

• [orm] [bug]

  Fixed issue where an ORM-enabled select() construct would not render any CTEs added only via the Select.add_cte() method that were not otherwise referenced in the statement.

  References: #10167

examples

• [examples] [bug]

  The dogpile_caching examples have been updated for 2.0 style queries. Within the “caching query” logic itself there is one conditional added to differentiate between Query and select() when performing an invalidation operation.

engine

• [engine] [bug]

  Fixed critical issue where setting create_engine.isolation_level to AUTOCOMMIT (as opposed to using the Engine.execution_options() method) would fail to restore “autocommit” to a pooled connection if an alternate isolation level were temporarily selected using Connection.execution_options.isolation_level.

  References: #10147

sql

• [sql] [bug]

  Fixed issue where unpickling of a Column or other ColumnElement would fail to restore the correct “comparator” object, which is used to generate SQL expressions specific to the type object.

  This change is also backported to: 1.4.50

  References: #10213

typing

• [typing] [usecase]

  Added new typing only utility functions Nullable() and NotNullable() to type a column or ORM class as, respectively, nullable or not nullable. These function are no-op at runtime, returning the input unchanged.

  References: #10173

• [typing] [bug]

  Typing improvements:

  • CursorResult is returned for some forms of Session.execute() where DML without RETURNING is used

  • fixed type for Query.with_for_update.of parameter within Query.with_for_update()

  • improvements to _DMLColumnArgument type used by some DML methods to pass column expressions

  • Add overload to literal() so that it is inferred that the return type is BindParameter[NullType] where literal.type_ param is None

  • Add overloads to ColumnElement.op() so that the inferred type when ColumnElement.op.return_type is not provided is Callable[[Any], BinaryExpression[Any]]

  • Add missing overload to ColumnElement.__add__()

  Pull request courtesy Mehdi Gmira.

  References: #9185

• [typing] [bug]

  Fixed issue in Session and AsyncSession methods such as Session.connection() where the Session.connection.execution_options parameter were hardcoded to an internal type that is not user-facing.

  References: #10182

asyncio

• [asyncio] [usecase]

  Added new methods AsyncConnection.aclose() as a synonym for AsyncConnection.close() and AsyncSession.aclose() as a synonym for AsyncSession.close() to the AsyncConnection and AsyncSession objects, to provide compatibility with Python standard library @contextlib.aclosing construct. Pull request courtesy Grigoriev Semyon.

  References: #9698

mysql

• [mysql] [usecase]

  Updated aiomysql dialect since the dialect appears to be maintained again. Re-added to the ci testing using version 0.2.0.

  This change is also backported to: 1.4.50

2.0.19

Released: July 15, 2023

orm

• [orm] [bug]

  Fixed issue where setting a relationship collection directly, where an object in the new collection were already present, would not trigger a cascade event for that object, leading to it not being added to the Session if it were not already present. This is similar in nature to #6471 and is a more apparent issue due to the removal of cascade_backrefs in the 2.0 series. The AttributeEvents.append_wo_mutation() event added as part of #6471 is now also emitted for existing members of a collection that are present in a bulk set of that same collection.

  References: #10089

• [orm] [bug]

  Fixed issue where objects that were associated with an unloaded collection via backref, but were not merged into the Session due to the removal of cascade_backrefs in the 2.0 series, would not emit a warning that these objects were not being included in a flush, even though they were pending members of the collection; in other such cases, a warning is emitted when a collection being flushed contains non-attached objects which will be essentially discarded. The addition of the warning for backref-pending collection members establishes greater consistency with collections that may be present or non-present and possibly flushed or not flushed at different times based on different relationship loading strategies.

  References: #10090

• [orm] [bug] [regression]

  Fixed additional regression caused by #9805 where more aggressive propagation of the “ORM” flag on statements could lead to an internal attribute error when embedding an ORM Query construct that nonetheless contained no ORM entities within a Core SQL statement, in this case ORM-enabled UPDATE and DELETE statements.

  References: #10098

engine

• [engine] [bug]

  Renamed Row.t and Row.tuple() to Row._t and Row._tuple(); this is to suit the policy that all methods and pre-defined attributes on Row should be in the style of Python standard library namedtuple where all fixed names have a leading underscore, to avoid name conflicts with existing column names. The previous method/attribute is now deprecated and will emit a deprecation warning.

  References: #10093

• [engine] [bug]

  Added detection for non-string, non-URL objects to the make_url() function, allowing ArgumentError to be thrown immediately, rather than causing failures later on. Special logic ensures that mock forms of URL are allowed through. Pull request courtesy Grigoriev Semyon.

  References: #10079

postgresql

• [postgresql] [bug]

  Fixed regression caused by improvements to PostgreSQL URL parsing in #10004 where “host” query string arguments that had colons in them, to support various third party proxy servers and/or dialects, would not parse correctly as these were evaluted as host:port combinations. Parsing has been updated to consider a colon as indicating a host:port value only if the hostname contains only alphanumeric characters with dots or dashes only (e.g. no slashes), followed by exactly one colon followed by an all-integer token of zero or more integers. In all other cases, the full string is taken as a host.

  References: #10069

• [postgresql] [bug]

  Fixed issue where comparisons to the CITEXT datatype would cast the right side to VARCHAR, leading to the right side not being interpreted as a CITEXT datatype, for the asyncpg, psycopg3 and pg80000 dialects. This led to the CITEXT type being essentially unusable for practical use; this is now fixed and the test suite has been corrected to properly assert that expressions are rendered correctly.

  References: #10096

2.0.18

Released: July 5, 2023

engine

• [engine] [bug]

  Adjusted the create_engine.schema_translate_map feature such that all schema names in the statement are now tokenized, regardless of whether or not a specific name is in the immediate schema translate map given, and to fallback to substituting the original name when the key is not in the actual schema translate map at execution time. These two changes allow for repeated use of a compiled object with schema schema_translate_maps that include or dont include various keys on each run, allowing cached SQL constructs to continue to function at runtime when schema translate maps with different sets of keys are used each time. In addition, added detection of schema_translate_map dictionaries which gain or lose a None key across calls for the same statement, which affects compilation of the statement and is not compatible with caching; an exception is raised for these scenarios.

  References: #10025

sql

• [sql] [bug]

  Fixed issue where the ColumnOperators.regexp_match() when using “flags” would not produce a “stable” cache key, that is, the cache key would keep changing each time causing cache pollution. The same issue existed for ColumnOperators.regexp_replace() with both the flags and the actual replacement expression. The flags are now represented as fixed modifier strings rendered as safestrings rather than bound parameters, and the replacement expression is established within the primary portion of the “binary” element so that it generates an appropriate cache key.

  Note that as part of this change, the ColumnOperators.regexp_match.flags and ColumnOperators.regexp_replace.flags have been modified to render as literal strings only, whereas previously they were rendered as full SQL expressions, typically bound parameters. These parameters should always be passed as plain Python strings and not as SQL expression constructs; it’s not expected that SQL expression constructs were used in practice for this parameter, so this is a backwards-incompatible change.

  The change also modifies the internal structure of the expression generated, for ColumnOperators.regexp_replace() with or without flags, and for ColumnOperators.regexp_match() with flags. Third party dialects which may have implemented regexp implementations of their own (no such dialects could be located in a search, so impact is expected to be low) would need to adjust the traversal of the structure to accommodate.

  This change is also backported to: 1.4.49

  References: #10042

• [sql] [bug]

  Fixed issue in mostly-internal CacheKey construct where the __ne__() operator were not properly implemented, leading to nonsensical results when comparing CacheKey instances to each other.

  This change is also backported to: 1.4.49

extensions

• [extensions] [usecase]

  Added new option to association_proxy() association_proxy.create_on_none_assignment; when an association proxy which refers to a scalar relationship is assigned the value None, and the referenced object is not present, a new object is created via the creator. This was apparently an undefined behavior in the 1.2 series that was silently removed.

  References: #10013

typing

• [typing] [usecase]

  Improved typing when using standalone operator functions from sqlalchemy.sql.operators such as sqlalchemy.sql.operators.eq.

  References: #10054

• [typing] [bug]

  Fixed some of the typing within the aliased() construct to correctly accept a Table object that’s been aliased with Table.alias(), as well as general support for FromClause objects to be passed as the “selectable” argument, since this is all supported.

  References: #10061

postgresql

• [postgresql] [usecase]

  Added multi-host support for the asyncpg dialect. General improvements and error checking added to the PostgreSQL URL routines for the “multihost” use case added as well. Pull request courtesy Ilia Dmitriev.

  See also

  Multihost Connections

  References: #10004

• [postgresql] [bug]

  Added new parameter native_inet_types=False to all PostgreSQL dialects, which indicates converters used by the DBAPI to convert rows from PostgreSQL INET and CIDR columns into Python ipaddress datatypes should be disabled, returning strings instead. This allows code written to work with strings for these datatypes to be migrated to asyncpg, psycopg, or pg8000 without code changes other than adding this parameter to the create_engine() or create_async_engine() function call.

  See also

  Network Data Types

  References: #9945

mariadb

• [mariadb] [usecase] [reflection]

  Allowed reflecting UUID columns from MariaDB. This allows Alembic to properly detect the type of such columns in existing MariaDB databases.

  References: #10028

mssql

• [mssql] [usecase]

  Added support for creation and reflection of COLUMNSTORE indexes in MSSQL dialect. Can be specified on indexes specifying mssql_columnstore=True.

  References: #7340

• [mssql] [bug] [sql]

  Fixed issue where performing Cast to a string type with an explicit collation would render the COLLATE clause inside the CAST function, which resulted in a syntax error.

  References: #9932

2.0.17

Released: June 23, 2023

orm

• [orm] [bug] [regression]

  Fixed regression in the 2.0 series where a query that used undefer_group() with selectinload() or subqueryload() would raise an AttributeError. Pull request courtesy of Matthew Martin.

  References: #9870

• [orm] [bug]

  Fixed issue in ORM Annotated Declarative which prevented a declared_attr from being used on a mixin which did not return a Mapped datatype, and instead returned a supplemental ORM datatype such as AssociationProxy. The Declarative runtime would erroneously try to interpret this annotation as needing to be Mapped and raise an error.

  References: #9957

• [orm] [bug] [typing]

  Fixed typing issue where using the AssociationProxy return type from a declared_attr function was disallowed.

  References: #9957

• [orm] [bug] [regression]

  Fixed regression introduced in 2.0.16 by #9879 where passing a callable to the mapped_column.default parameter of mapped_column while also setting init=False would interpret this value as a Dataclass default value which would be assigned directly to new instances of the object directly, bypassing the default generator taking place as the Column.default value generator on the underlying Column. This condition is now detected so that the previous behavior is maintained, however a deprecation warning for this ambiguous use is emitted; to populate the default generator for a Column, the mapped_column.insert_default parameter should be used, which disambiguates from the mapped_column.default parameter whose name is fixed as per pep-681.

  References: #9936

• [orm] [bug]

  Additional hardening and documentation for the ORM Session “state change” system, which detects concurrent use of Session and AsyncSession objects; an additional check is added within the process to acquire connections from the underlying engine, which is a critical section with regards to internal connection management.

  References: #9973

• [orm] [bug]

  Fixed issue in ORM loader strategy logic which further allows for long chains of contains_eager() loader options across complex inheriting polymorphic / aliased / of_type() relationship chains to take proper effect in queries.

  References: #10006

• [orm] [bug]

  Fixed issue in support for the Enum datatype in the registry.type_annotation_map first added as part of #8859 where using a custom Enum with fixed configuration in the map would fail to transfer the Enum.name parameter, which among other issues would prevent PostgreSQL enums from working if the enum values were passed as individual values. Logic has been updated so that “name” is transferred over, but also that the default Enum which is against the plain Python enum.Enum class or other “empty” enum won’t set a hardcoded name of "enum" either.

  References: #9963

orm declarative

• [orm] [declarative] [bug]

  A warning is emitted when an ORM relationship() and other MapperProperty objects are assigned to two different class attributes at once; only one of the attributes will be mapped. A warning for this condition was already in place for Column and mapped_column objects.

  References: #3532

extensions

• [extensions] [bug]

  Fixed issue in mypy plugin for use with mypy 1.4.

  This change is also backported to: 1.4.49

typing

• [typing] [bug]

  Fixed typing issue which prevented WriteOnlyMapped and DynamicMapped attributes from being used fully within ORM queries.

  References: #9985

postgresql

• [postgresql] [usecase]

  The pg8000 dialect now supports RANGE and MULTIRANGE datatypes, using the existing RANGE API described at Range and Multirange Types. Range and multirange types are supported in the pg8000 driver from version 1.29.8. Pull request courtesy Tony Locke.

  References: #9965

2.0.16

Released: June 10, 2023

platform

• [platform] [usecase]

  Compatibility improvements allowing the complete test suite to pass on Python 3.12.0b1.

orm

• [orm] [usecase]

  Improved DeferredReflection.prepare() to accept arbitrary **kw arguments that are passed to MetaData.reflect(), allowing use cases such as reflection of views as well as dialect-specific arguments to be passed. Additionally, modernized the DeferredReflection.prepare.bind argument so that either an Engine or Connection are accepted as the “bind” argument.

  References: #9828

• [orm] [bug]

  Fixed issue where DeclarativeBaseNoMeta declarative base class would not function with non-mapped mixins or abstract classes, raising an AttributeError instead.

  References: #9862

• [orm] [bug] [regression]

  Fixed regression in the 2.0 series where the default value of validates.include_backrefs got changed to False for the validates() function. This default is now restored to True.

  References: #9820

• [orm] [bug]

  Fixed bug in new feature which allows a WHERE clause to be used in conjunction with ORM Bulk UPDATE by Primary Key, added in version 2.0.11 as part of #9583, where sending dictionaries that did not include the primary key values for each row would run through the bulk process and include “pk=NULL” for the rows, silently failing. An exception is now raised if primary key values for bulk UPDATE are not supplied.

  References: #9917

• [orm] [bug] [dataclasses]

  Fixed an issue where generating dataclasses fields that specified a default value and set init=False would not work. The dataclasses behavior in this case is to set the default value on the class, that’s not compatible with the descriptors used by SQLAlchemy. To support this case the default is transformed to a default_factory when generating the dataclass.

  References: #9879

• [orm] [bug]

  A deprecation warning is emitted whenever a property is added to a Mapper where an ORM mapped property were already configured, or an attribute is already present on the class. Previously, there was a non-deprecation warning for this case that did not emit consistently. The logic for this warning has been improved so that it detects end-user replacement of attribute while not having false positives for internal Declarative and other cases where replacement of descriptors with new ones is expected.

  References: #9841

• [orm] [bug]

  Improved the argument chacking on the map_imperatively.local_table parameter of the registry.map_imperatively() method, ensuring only a Table or other FromClause is passed, and not an existing mapped class, which would lead to undefined behavior as the object were further interpreted for a new mapping.

  References: #9869

• [orm] [bug]

  The InstanceState.unloaded_expirable attribute is a synonym for InstanceState.unloaded, and is now deprecated; this attribute was always implementation-specific and should not have been public.

  References: #9913

asyncio

• [asyncio] [usecase]

  Added new create_async_engine.async_creator parameter to create_async_engine(), which accomplishes the same purpose as the create_engine.creator parameter of create_engine(). This is a no-argument callable that provides a new asyncio connection, using the asyncio database driver directly. The create_async_engine() function will wrap the driver-level connection in the appropriate structures. Pull request courtesy of Jack Wotherspoon.

  References: #8215

postgresql

• [postgresql] [usecase] [reflection]

  Cast NAME columns to TEXT when using ARRAY_AGG in PostgreSQL reflection. This seems to improve compatibility with some PostgreSQL derivatives that may not support aggregations on the NAME type.

  References: #9838

• [postgresql] [usecase]

  Unified the custom PostgreSQL operator definitions, since they are shared among multiple different data types.

  References: #9041

• [postgresql] [usecase]

  Added support for PostgreSQL 10 NULLS NOT DISTINCT feature of unique indexes and unique constraint using the dialect option postgresql_nulls_not_distinct. Updated the reflection logic to also correctly take this option into account. Pull request courtesy of Pavel Siarchenia.

  References: #8240

• [postgresql] [bug]

  Use proper precedence on PostgreSQL specific operators, such as @>. Previously the precedence was wrong, leading to wrong parenthesis when rendering against and ANY or ALL construct.

  References: #9836

• [postgresql] [bug]

  Fixed issue where the ColumnOperators.like.escape and similar parameters did not allow an empty string as an argument that would be passed through as the “escape” character; this is a supported syntax by PostgreSQL. Pull requset courtesy Martin Caslavsky.

  References: #9907

2.0.15

Released: May 19, 2023

orm

• [orm] [bug]

  As more projects are using new-style “2.0” ORM querying, it’s becoming apparent that the conditional nature of “autoflush”, being based on whether or not the given statement refers to ORM entities, is becoming more of a key behavior. Up until now, the “ORM” flag for a statement has been loosely based around whether or not the statement returns rows that correspond to ORM entities or columns; the original purpose of the “ORM” flag was to enable ORM-entity fetching rules which apply post-processing to Core result sets as well as ORM loader strategies to the statement. For statements that don’t build on rows that contain ORM entities, the “ORM” flag was considered to be mostly unnecessary.

  It still may be the case that “autoflush” would be better taking effect for all usage of Session.execute() and related methods, even for purely Core SQL constructs. However, this still could impact legacy cases where this is not expected and may be more of a 2.1 thing. For now however, the rules for the “ORM-flag” have been opened up so that a statement that includes ORM entities or attributes anywhere within, including in the WHERE / ORDER BY / GROUP BY clause alone, within scalar subqueries, etc. will enable this flag. This will cause “autoflush” to occur for such statements and also be visible via the ORMExecuteState.is_orm_statement event-level attribute.

  References: #9805

postgresql

• [postgresql] [bug] [regression]

  Repaired the base Uuid datatype for the PostgreSQL dialect to make full use of the PG-specific UUID dialect-specific datatype when “native_uuid” is selected, so that PG driver behaviors are included. This issue became apparent due to the insertmanyvalues improvement made as part of #9618, where in a similar manner as that of #9739, the asyncpg driver is very sensitive to datatype casts being present or not, and the PostgreSQL driver-specific native UUID datatype must be invoked when this generic type is used so that these casts take place.

  References: #9808

2.0.14

Released: May 18, 2023

orm

• [orm] [bug]

  Modified the JoinedLoader implementation to use a simpler approach in one particular area where it previously used a cached structure that would be shared among threads. The rationale is to avoid a potential race condition which is suspected of being the cause of a particular crash that’s been reported multiple times. The cached structure in question is still ultimately “cached” via the compiled SQL cache, so a performance degradation is not anticipated.

  References: #9777

• [orm] [bug] [regression]

  Fixed regression where use of update() or delete() within a CTE construct, then used in a select(), would raise a CompileError as a result of ORM related rules for performing ORM-level update/delete statements.

  References: #9767

• [orm] [bug]

  Fixed issue in new ORM Annotated Declarative where using a ForeignKey (or other column-level constraint) inside of mapped_column() which is then copied out to models via pep-593 Annotated would apply duplicates of each constraint to the Column as produced in the target Table, leading to incorrect CREATE TABLE DDL as well as migration directives under Alembic.

  References: #9766

• [orm] [bug]

  Fixed issue where using additional relationship criteria with the joinedload() loader option, where the additional criteria itself contained correlated subqueries that referred to the joined entities and therefore also required “adaption” to aliased entities, would be excluded from this adaption, producing the wrong ON clause for the joinedload.

  References: #9779

sql

• [sql] [usecase]

  Generalized the MSSQL try_cast() function into the sqlalchemy. import namespace so that it may be implemented by third party dialects as well. Within SQLAlchemy, the try_cast() function remains a SQL Server-only construct that will raise CompileError if used with backends that don’t support it.

  try_cast() implements a CAST where un-castable conversions are returned as NULL, instead of raising an error. Theoretically, the construct could be implemented by third party dialects for Google BigQuery, DuckDB, and Snowflake, and possibly others.

  Pull request courtesy Nick Crews.

  References: #9752

• [sql] [bug]

  Fixed issue in values() construct where an internal compilation error would occur if the construct were used inside of a scalar subquery.

  References: #9772

postgresql

• [postgresql] [bug]

  Fixed apparently very old issue where the ENUM.create_type parameter, when set to its non-default of False, would not be propagated when the Column which it’s a part of were copied, as is common when using ORM Declarative mixins.

  References: #9773

tests

• [tests] [bug] [pypy]

  Fixed test that relied on the sys.getsizeof() function to not run on pypy, where this function appears to have different behavior than it does on cpython.

  References: #9789

2.0.13

Released: May 10, 2023

orm

• [orm] [bug]

  Fixed issue where ORM Annotated Declarative would not resolve forward references correctly in all cases; in particular, when using from __future__ import annotations in combination with Pydantic dataclasses.

  References: #9717

• [orm] [bug]

  Fixed issue in new Using RETURNING with upsert statements feature where the populate_existing execution option was not being propagated to the loading option, preventing existing attributes from being refreshed in-place.

  References: #9746

• [orm] [bug]

  Fixed loader strategy pathing issues where eager loaders such as joinedload() / selectinload() would fail to traverse fully for many-levels deep following a load that had a with_polymorphic() or similar construct as an interim member.

  References: #9715

• [orm] [bug]

  Fixed issue in mapped_column() construct where the correct warning for “column X named directly multiple times” would not be emitted when ORM mapped attributes referred to the same Column, if the mapped_column() construct were involved, raising an internal assertion instead.

  References: #9630

sql

• [sql] [usecase]

  Implemented the “cartesian product warning” for UPDATE and DELETE statements, those which include multiple tables that are not correlated together in some way.

  References: #9721

• [sql] [bug]

  Fixed the base class for dialect-specific float/double types; Oracle BINARY_DOUBLE now subclasses Double, and internal types for Float for asyncpg and pg8000 now correctly subclass Float.

• [sql] [bug]

  Fixed issue where update() construct that included multiple tables and no VALUES clause would raise with an internal error. Current behavior for Update with no values is to generate a SQL UPDATE statement with an empty “set” clause, so this has been made consistent for this specific sub-case.

schema

• [schema] [performance]

  Improved how table columns are added, avoiding unnecessary allocations, significantly speeding up the creation of many table, like when reflecting entire schemas.

  References: #9597

typing

• [typing] [bug]

  Fixed typing for the Session.get.with_for_update parameter of Session.get() and Session.refresh() (as well as corresponding methods on AsyncSession) to accept boolean True and all other argument forms accepted by the parameter at runtime.

  References: #9762

• [typing] [sql]

  Added type ColumnExpressionArgument as a public-facing type that indicates column-oriented arguments which are passed to SQLAlchemy constructs, such as Select.where(), and_() and others. This may be used to add typing to end-user functions which call these methods.

  References: #9656

asyncio

• [asyncio] [usecase]

  Added a new helper mixin AsyncAttrs that seeks to improve the use of lazy-loader and other expired or deferred ORM attributes with asyncio, providing a simple attribute accessor that provides an await interface to any ORM attribute, whether or not it needs to emit SQL.

  See also

  AsyncAttrs

  References: #9731

• [asyncio] [bug]

  Fixed issue in semi-private await_only() and await_fallback() concurrency functions where the given awaitable would remain un-awaited if the function threw a GreenletError, which could cause “was not awaited” warnings later on if the program continued. In this case, the given awaitable is now cancelled before the exception is thrown.

postgresql

• [postgresql] [bug] [regression]

  Fixed another regression due to the “insertmanyvalues” change in 2.0.10 as part of #9618, in a similar way as regression #9701, where LargeBinary datatypes also need additional casts on when using the asyncpg driver specifically in order to work with the new bulk INSERT format.

  References: #9739

oracle

• [oracle] [reflection]

  Added reflection support in the Oracle dialect to expression based indexes and the ordering direction of index expressions.

  References: #9597

misc

• [bug] [ext]

  Fixed issue in Mutable where event registration for ORM mapped attributes would be called repeatedly for mapped inheritance subclasses, leading to duplicate events being invoked in inheritance hierarchies.

  References: #9676

2.0.12

Released: April 30, 2023

orm

• [orm] [bug]

  Fixed critical caching issue where the combination of aliased() and hybrid_property() expression compositions would cause a cache key mismatch, leading to cache keys that held onto the actual aliased() object while also not matching that of equivalent constructs, filling up the cache.

  This change is also backported to: 1.4.48

  References: #9728

mysql

• [mysql] [bug] [mariadb]

  Fixed issues regarding reflection of comments for Table and Column objects, where the comments contained control characters such as newlines. Additional testing support for these characters as well as extended Unicode characters in table and column comments (the latter of which aren’t supported by MySQL/MariaDB) added to testing overall.

  References: #9722

2.0.11

Released: April 26, 2023

orm

• [orm] [usecase]

  The ORM bulk INSERT and UPDATE features now add these capabilities:

  • The requirement that extra parameters aren’t passed when using ORM INSERT using the “orm” dml_strategy setting is lifted.

  • The requirement that additional WHERE criteria is not passed when using ORM UPDATE using the “bulk” dml_strategy setting is lifted. Note that in this case, the check for expected row count is turned off.

  References: #9583, #9595

• [orm] [bug]

  Fixed 2.0 regression where use of bindparam() inside of Insert.values() would fail to be interpreted correctly when executing the Insert statement using the ORM Session, due to the new ORM-enabled insert feature not implementing this use case.

  References: #9583, #9595

engine

• [engine] [performance]

  A series of performance enhancements to Row:

  • __getattr__ performance of the row’s “named tuple” interface has been improved; within this change, the Row implementation has been streamlined, removing constructs and logic that were specific to the 1.4 and prior series of SQLAlchemy. As part of this change, the serialization format of Row has been modified slightly, however rows which were pickled with previous SQLAlchemy 2.0 releases will be recognized within the new format. Pull request courtesy J. Nick Koston.

  • Improved row processing performance for “binary” datatypes by making the “bytes” handler conditional on a per driver basis. As a result, the “bytes” result handler has been removed for nearly all drivers other than psycopg2, all of which in modern forms support returning Python “bytes” directly. Pull request courtesy J. Nick Koston.

  • Additional refactorings inside of Row to improve performance by Federico Caselli.

  References: #9678, #9680

• [engine] [bug] [regression]

  Fixed regression which prevented the URL.normalized_query attribute of URL from functioning.

  References: #9682

sql

• [sql] [usecase]

  Added support for slice access with ColumnCollection, e.g. table.c[0:5], subquery.c[:-1] etc. Slice access returns a sub ColumnCollection in the same way as passing a tuple of keys. This is a natural continuation of the key-tuple access added for #8285, where it appears to be an oversight that the slice access use case was omitted.

  References: #8285

typing

• [typing] [bug]

  Improved typing of RowMapping to indicate that it support also Column as index objects, not only string names. Pull request courtesy Andy Freeland.

  References: #9644

postgresql

• [postgresql] [bug] [regression]

  Fixed critical regression caused by #9618, which modified the architecture of the insertmanyvalues feature for 2.0.10, which caused floating point values to lose all decimal places when being inserted using the insertmanyvalues feature with either the psycopg2 or psycopg drivers.

  References: #9701

mssql

• [mssql] [bug]

  Implemented the Double type for SQL Server, where it will render DOUBLE PRECISION at DDL time. This is implemented using a new MSSQL datatype DOUBLE_PRECISION which also may be used directly.

oracle

• [oracle] [bug]

  Fixed issue in Oracle dialects where Decimal returning types such as Numeric would return floating point values, rather than Decimal objects, when these columns were used in the Insert.returning() clause to return INSERTed values.

2.0.10

Released: April 21, 2023

orm

• [orm] [bug]

  Fixed bug where various ORM-specific getters such as ORMExecuteState.is_column_load, ORMExecuteState.is_relationship_load, ORMExecuteState.loader_strategy_path etc. would throw an AttributeError if the SQL statement itself were a “compound select” such as a UNION.

  This change is also backported to: 1.4.48

  References: #9634

• [orm] [bug]

  Fixed issue where the declared_attr.directive() modifier was not correctly honored for subclasses when applied to the __mapper_args__ special method name, as opposed to direct use of declared_attr. The two constructs should have identical runtime behaviors.

  References: #9625

• [orm] [bug]

  Made an improvement to the with_loader_criteria() loader option to allow it to be indicated in the Executable.options() method of a top-level statement that is not itself an ORM statement. Examples include select() that’s embedded in compound statements such as union(), within an Insert.from_select() construct, as well as within CTE expressions that are not ORM related at the top level.

  References: #9635

• [orm] [bug]

  Fixed bug in ORM bulk insert feature where additional unnecessary columns would be rendered in the INSERT statement if RETURNING of individual columns were requested.

  References: #9685

• [orm] [bug]

  Fixed bug in ORM Declarative Dataclasses where the query_expression() and column_property() constructs, which are documented as read-only constructs in the context of a Declarative mapping, could not be used with a MappedAsDataclass class without adding init=False, which in the case of query_expression() was not possible as no init parameter was included. These constructs have been modified from a dataclass perspective to be assumed to be “read only”, setting init=False by default and no longer including them in the pep-681 constructor. The dataclass parameters for column_property() init, default, default_factory, kw_only are now deprecated; these fields don’t apply to column_property() as used in a Declarative dataclasses configuration where the construct would be read-only. Also added read-specific parameter query_expression.compare to query_expression(); query_expression.repr was already present.

  References: #9628

• [orm] [bug]

  Added missing mapped_column.active_history parameter to mapped_column() construct.

engine

• [engine] [usecase]

  Added create_pool_from_url() and create_async_pool_from_url() to create a Pool instance from an input url passed as string or URL.

  References: #9613

• [engine] [bug]

  Repaired a major shortcoming which was identified in the “Insert Many Values” Behavior for INSERT statements performance optimization feature first introduced in the 2.0 series. This was a continuation of the change in 2.0.9 which disabled the SQL Server version of the feature due to a reliance in the ORM on apparent row ordering that is not guaranteed to take place. The fix applies new logic to all “insertmanyvalues” operations, which takes effect when a new parameter Insert.returning.sort_by_parameter_order on the Insert.returning() or UpdateBase.return_defaults() methods, that through a combination of alternate SQL forms, direct correspondence of client side parameters, and in some cases downgrading to running row-at-a-time, will apply sorting to each batch of returned rows using correspondence to primary key or other unique values in each row which can be correlated to the input data.

  Performance impact is expected to be minimal as nearly all common primary key scenarios are suitable for parameter-ordered batching to be achieved for all backends other than SQLite, while “row-at-a-time” mode operates with a bare minimum of Python overhead compared to the very heavyweight approaches used in the 1.x series. For SQLite, there is no difference in performance when “row-at-a-time” mode is used.

  It’s anticipated that with an efficient “row-at-a-time” INSERT with RETURNING batching capability, the “insertmanyvalues” feature can be later be more easily generalized to third party backends that include RETURNING support but not necessarily easy ways to guarantee a correspondence with parameter order.

  See also

  Correlating RETURNING rows to parameter sets

  References: #9603, #9618

typing

• [typing] [bug]

  Added typing information for recently added operators ColumnOperators.icontains(), ColumnOperators.istartswith(), ColumnOperators.iendswith(), and bitwise operators ColumnOperators.bitwise_and(), ColumnOperators.bitwise_or(), ColumnOperators.bitwise_xor(), ColumnOperators.bitwise_not(), ColumnOperators.bitwise_lshift() ColumnOperators.bitwise_rshift(). Pull request courtesy Martijn Pieters.

  References: #9650

• [typing] [bug]

  Updates to the codebase to pass typing with Mypy 1.2.0.

• [typing] [bug]

  Fixed typing issue where PropComparator.and_() expressions would not be correctly typed inside of loader options such as selectinload().

  References: #9669

postgresql

• [postgresql] [usecase]

  Added prepared_statement_name_func connection argument option in the asyncpg dialect. This option allows passing a callable used to customize the name of the prepared statement that will be created by the driver when executing queries. Pull request courtesy Pavel Sirotkin.

  See also

  Prepared Statement Name

  References: #9608

• [postgresql] [usecase]

  Add missing Range.intersection() method. Pull request courtesy Yurii Karabas.

  References: #9509

• [postgresql] [bug]

  Restored the ENUM.name parameter as optional in the signature for ENUM, as this is chosen automatically from a given pep-435 Enum type.

  References: #9611

• [postgresql] [bug]

  Fixed issue where the comparison for ENUM against a plain string would cast that right-hand side type as VARCHAR, which due to more explicit casting added to dialects such as asyncpg would produce a PostgreSQL type mismatch error.

  References: #9621

• [postgresql] [bug]

  Fixed issue that prevented reflection of expression based indexes with long expressions in PostgreSQL. The expression where erroneously truncated to the identifier length (that’s 63 bytes by default).

  References: #9615

mssql

• [mssql] [bug]

  Restored the insertmanyvalues feature for Microsoft SQL Server. This feature was disabled in version 2.0.9 due to an apparent reliance on the ordering of RETURNING that is not guaranteed. The architecture of the “insertmanyvalues” feature has been reworked to accommodate for specific organizations of INSERT statements and result row handling that can guarantee the correspondence of returned rows to input records.

  See also

  Correlating RETURNING rows to parameter sets

  References: #9603, #9618

oracle

• [oracle] [bug]

  Fixed issue where the Uuid datatype could not be used in an INSERT..RETURNING clause with the Oracle dialect.

2.0.9

Released: April 5, 2023

orm

• [orm] [bug]

  Fixed endless loop which could occur when using “relationship to aliased class” feature and also indicating a recursive eager loader such as lazy="selectinload" in the loader, in combination with another eager loader on the opposite side. The check for cycles has been fixed to include aliased class relationships.

  This change is also backported to: 1.4.48

  References: #9590

mariadb

• [mariadb] [bug]

  Added row_number as reserved word in MariaDb.

  References: #9588

mssql

• [mssql] [bug]

  The SQLAlchemy “insertmanyvalues” feature which allows fast INSERT of many rows while also supporting RETURNING is temporarily disabled for SQL Server. As the unit of work currently relies upon this feature such that it matches existing ORM objects to returned primary key identities, this particular use pattern does not work with SQL Server in all cases as the order of rows returned by “OUTPUT inserted” may not always match the order in which the tuples were sent, leading to the ORM making the wrong decisions about these objects in subsequent operations.

  The feature will be re-enabled in an upcoming release and will again take effect for multi-row INSERT statements, however the unit-of-work’s use of the feature will be disabled, possibly for all dialects, unless ORM-mapped tables also include a “sentinel” column so that the returned rows can be referenced back to the original data passed in.

  References: #9603

• [mssql] [bug]

  Changed the bulk INSERT strategy used for SQL Server “executemany” with pyodbc when fast_executemany is set to True by using fast_executemany / cursor.executemany() for bulk INSERT that does not include RETURNING, restoring the same behavior as was used in SQLAlchemy 1.4 when this parameter is set.

  New performance details from end users have shown that fast_executemany is still much faster for very large datasets as it uses ODBC commands that can receive all rows in a single round trip, allowing for much larger datasizes than the batches that can be sent by “insertmanyvalues” as was implemented for SQL Server.

  While this change was made such that “insertmanyvalues” continued to be used for INSERT that includes RETURNING, as well as if fast_executemany were not set, due to #9603, the “insertmanyvalues” strategy has been disabled for SQL Server across the board in any case.

  References: #9586

2.0.8

Released: March 31, 2023

orm

• [orm] [usecase]

  Exceptions such as TypeError and ValueError raised by Python dataclasses when making use of the MappedAsDataclass mixin class or registry.mapped_as_dataclass() decorator are now wrapped within an InvalidRequestError wrapper along with informative context about the error message, referring to the Python dataclasses documentation as the authoritative source of background information on the cause of the exception.

  See also

  Python dataclasses error encountered when creating dataclass for <classname>

  References: #9563

• [orm] [bug]

  Fixed issue in ORM Annotated Declarative where using a recursive type (e.g. using a nested Dict type) would result in a recursion overflow in the ORM’s annotation resolution logic, even if this datatype were not necessary to map the column.

  References: #9553

• [orm] [bug]

  Fixed issue where the mapped_column() construct would raise an internal error if used on a Declarative mixin and included the mapped_column.deferred parameter.

  References: #9550

• [orm] [bug]

  Expanded the warning emitted when a plain column() object is present in a Declarative mapping to include any arbitrary SQL expression that is not declared within an appropriate property type such as column_property(), deferred(), etc. These attributes are otherwise not mapped at all and remain unchanged within the class dictionary. As it seems likely that such an expression is usually not what’s intended, this case now warns for all such otherwise ignored expressions, rather than just the column() case.

  References: #9537

• [orm] [bug]

  Fixed regression where accessing the expression value of a hybrid property on a class that was either unmapped or not-yet-mapped (such as calling upon it within a declared_attr() method) would raise an internal error, as an internal fetch for the parent class’ mapper would fail and an instruction for this failure to be ignored were inadvertently removed in 2.0.

  References: #9519

• [orm] [bug]

  Fields that are declared on Declarative Mixins and then combined with classes that make use of MappedAsDataclass, where those mixin fields are not themselves part of a dataclass, now emit a deprecation warning as these fields will be ignored in a future release, as Python dataclasses behavior is to ignore these fields. Type checkers will not see these fields under pep-681.

  See also

  When transforming <cls> to a dataclass, attribute(s) originate from superclass <cls> which is not a dataclass. - background on rationale

  Using mixins and abstract superclasses

  References: #9350

• [orm] [bug]

  Fixed issue where the BindParameter.render_literal_execute() method would fail when called on a parameter that also had ORM annotations associated with it. In practice, this would be observed as a failure of SQL compilation when using some combinations of a dialect that uses “FETCH FIRST” such as Oracle along with a Select construct that uses Select.limit(), within some ORM contexts, including if the statement were embedded within a relationship primaryjoin expression.

  References: #9526

• [orm] [bug]

  Towards maintaining consistency with unit-of-work changes made for #5984 and #8862, both of which disable “lazy=’raise’” handling within Session processes that aren’t triggered by attribute access, the Session.delete() method will now also disable “lazy=’raise’” handling when it traverses relationship paths in order to process the “delete” and “delete-orphan” cascade rules. Previously, there was no easy way to generically call Session.delete() on an object that had “lazy=’raise’” set up such that only the necessary relationships would be loaded. As “lazy=’raise’” is primarily intended to catch SQL loading that emits on attribute access, Session.delete() is now made to behave like other Session methods including Session.merge() as well as Session.flush() along with autoflush.

  References: #9549

• [orm] [bug]

  Fixed issue where an annotation-only Mapped directive could not be used in a Declarative mixin class, without that attribute attempting to take effect for single- or joined-inheritance subclasses of mapped classes that had already mapped that attribute on a superclass, producing conflicting column errors and/or warnings.

  References: #9564

• [orm] [bug] [typing]

  Properly type Insert.from_select.names to accept a list of string or columns or mapped attributes.

  References: #9514

examples

• [examples] [bug]

  Fixed issue in “versioned history” example where using a declarative base that is derived from DeclarativeBase would fail to be mapped. Additionally, repaired the given test suite so that the documented instructions for running the example using Python unittest now work again.

typing

• [typing] [bug]

  Fixed typing for deferred() and query_expression() to work correctly with 2.0 style mappings.

  References: #9536

postgresql

• [postgresql] [bug]

  Fixed critical regression in PostgreSQL dialects such as asyncpg which rely upon explicit casts in SQL in order for datatypes to be passed to the driver correctly, where a String datatype would be cast along with the exact column length being compared, leading to implicit truncation when comparing a VARCHAR of a smaller length to a string of greater length regardless of operator in use (e.g. LIKE, MATCH, etc.). The PostgreSQL dialect now omits the length from VARCHAR when rendering these casts.

  References: #9511

mysql

• [mysql] [bug]

  Fixed issue where string datatypes such as CHAR, VARCHAR, TEXT, as well as binary BLOB, could not be produced with an explicit length of zero, which has special meaning for MySQL. Pull request courtesy J. Nick Koston.

  References: #9544

misc

• [bug] [util]

  Implemented missing methods copy and pop in OrderedSet class.

  References: #9487

2.0.7

Released: March 18, 2023

typing

• [typing] [bug]

  Fixed typing issue where composite() would not allow an arbitrary callable as the source of the composite class.

  References: #9502

postgresql

• [postgresql] [usecase]

  Added new PostgreSQL type CITEXT. Pull request courtesy Julian David Rath.

  References: #9416

• [postgresql] [usecase]

  Modifications to the base PostgreSQL dialect to allow for better integration with the sqlalchemy-redshift third party dialect for SQLAlchemy 2.0. Pull request courtesy matthewgdv.

  References: #9442

2.0.6

Released: March 13, 2023

orm

• [orm] [bug]

  Fixed bug where the “active history” feature was not fully implemented for composite attributes, making it impossible to receive events that included the “old” value. This seems to have been the case with older SQLAlchemy versions as well, where “active_history” would be propagated to the underlying column-based attributes, but an event handler listening to the composite attribute itself would not be given the “old” value being replaced, even if the composite() were set up with active_history=True.

  Additionally, fixed a regression that’s local to 2.0 which disallowed active_history on composite from being assigned to the impl with attr.impl.active_history=True.

  References: #9460

• [orm] [bug]

  Fixed regression involving pickling of Python rows between the cython and pure Python implementations of Row, which occurred as part of refactoring code for version 2.0 with typing. A particular constant were turned into a string based Enum for the pure Python version of Row whereas the cython version continued to use an integer constant, leading to deserialization failures.

  References: #9418

sql

• [sql] [bug] [regression]

  Fixed regression where the fix for #8098, which was released in the 1.4 series and provided a layer of concurrency-safe checks for the lambda SQL API, included additional fixes in the patch that failed to be applied to the main branch. These additional fixes have been applied.

  References: #9461

• [sql] [bug]

  Fixed regression where the select() construct would not be able to render if it were given no columns and then used in the context of an EXISTS, raising an internal exception instead. While an empty “SELECT” is not typically valid SQL, in the context of EXISTS databases such as PostgreSQL allow it, and in any case the condition now no longer raises an internal exception.

  References: #9440

typing

• [typing] [bug]

  Fixed typing issue where ColumnElement.cast() did not allow a TypeEngine argument independent of the type of the ColumnElement itself, which is the purpose of ColumnElement.cast().

  References: #9451

• [typing] [bug]

  Fixed issues to allow typing tests to pass under Mypy 1.1.1.

oracle

• [oracle] [bug]

  Fixed reflection bug where Oracle “name normalize” would not work correctly for reflection of symbols that are in the “PUBLIC” schema, such as synonyms, meaning the PUBLIC name could not be indicated as lower case on the Python side for the Table.schema argument. Using uppercase “PUBLIC” would work, but would then lead to awkward SQL queries including a quoted "PUBLIC" name as well as indexing the table under uppercase “PUBLIC”, which was inconsistent.

  References: #9459

2.0.5.post1

Released: March 5, 2023

orm

• [orm] [bug]

  Added constructor arguments to the built-in mapping collection types including KeyFuncDict, attribute_keyed_dict(), column_keyed_dict() so that these dictionary types may be constructed in place given the data up front; this provides further compatibility with tools such as Python dataclasses .asdict() which relies upon invoking these classes directly as ordinary dictionary classes.

  References: #9418

• [orm] [bug] [regression]

  Fixed multiple regressions due to #8372, involving attribute_mapped_collection() (now called attribute_keyed_dict()).

  First, the collection was no longer usable with “key” attributes that were not themselves ordinary mapped attributes; attributes linked to descriptors and/or association proxy attributes have been fixed.

  Second, if an event or other operation needed access to the “key” in order to populate the dictionary from an mapped attribute that was not loaded, this also would raise an error inappropriately, rather than trying to load the attribute as was the behavior in 1.4. This is also fixed.

  For both cases, the behavior of #8372 has been expanded. #8372 introduced an error that raises when the derived key that would be used as a mapped dictionary key is effectively unassigned. In this change, a warning only is emitted if the effective value of the “.key” attribute is None, where it cannot be unambiguously determined if this None was intentional or not. None will be not supported as mapped collection dictionary keys going forward (as it typically refers to NULL which means “unknown”). Setting attribute_keyed_dict.ignore_unpopulated_attribute will now cause such None keys to be ignored as well.

  References: #9424

• [orm] [bug]

  Identified that the sqlite and mssql+pyodbc dialects are now compatible with the SQLAlchemy ORM’s “versioned rows” feature, since SQLAlchemy now computes rowcount for a RETURNING statement in this specific case by counting the rows returned, rather than relying upon cursor.rowcount. In particular, the ORM versioned rows use case (documented at Configuring a Version Counter) should now be fully supported with the SQL Server pyodbc dialect.

• [orm] [bug]

  Added support for the Mapper.polymorphic_load parameter to be applied to each mapper in an inheritance hierarchy more than one level deep, allowing columns to load for all classes in the hierarchy that indicate "selectin" using a single statement, rather than ignoring elements on those intermediary classes that nonetheless indicate they also would participate in "selectin" loading and were not part of the base-most SELECT statement.

  References: #9373

• [orm] [bug]

  Continued the fix for #8853, allowing the Mapped name to be fully qualified regardless of whether or not from __annotations__ import future were present. This issue first fixed in 2.0.0b3 confirmed that this case worked via the test suite, however the test suite apparently was not testing the behavior for the name Mapped not being locally present at all; string resolution has been updated to ensure the Mapped symbol is locatable as applies to how the ORM uses these functions.

  References: #8853, #9335

orm declarative

• [bug] [orm declarative]

  Fixed issue where new mapped_column.use_existing_column feature would not work if the two same-named columns were mapped under attribute names that were differently-named from an explicit name given to the column itself. The attribute names can now be differently named when using this parameter.

  References: #9332

engine

• [engine] [performance]

  A small optimization to the Cython implementation of Result using a cdef for a particular int value to avoid Python overhead. Pull request courtesy Matus Valo.

  References: #9343

• [engine] [bug]

  Fixed bug where Row objects could not be reliably unpickled across processes due to an accidental reliance on an unstable hash value.

  References: #9423

sql

• [sql] [bug] [regression]

  Restore the nullslast() and nullsfirst() legacy functions into the sqlalchemy import namespace. Previously, the newer nulls_last() and nulls_first() functions were available, but the legacy ones were inadvertently removed.

  References: #9390

schema

• [schema]

  Validate that when provided the MetaData.schema argument of MetaData is a string.

typing

• [typing] [usecase]

  Exported the type returned by scoped_session.query_property() using a new public type QueryPropertyDescriptor.

  References: #9338

• [typing] [bug]

  Fixed bug where the Connection.scalars() method was not typed as allowing a multiple-parameters list, which is now supported using insertmanyvalues operations.

• [typing] [bug]

  Improved typing for the mapping passed to Insert.values() and Update.values() to be more open-ended about collection type, by indicating read-only Mapping instead of writeable Dict which would error out on too limited of a key type.

  References: #9376

• [typing] [bug]

  Added missing init overload to the Numeric type object so that pep-484 type checkers may properly resolve the complete type, deriving from the Numeric.asdecimal parameter whether Decimal or float objects will be represented.

  References: #9391

• [typing] [bug]

  Fixed typing bug where Select.from_statement() would not accept text() or TextualSelect objects as a valid type. Additionally repaired the columns method to have a return type, which was missing.

  References: #9398

• [typing] [bug]

  Fixed typing issue where with_polymorphic() would not record the class type correctly.

  References: #9340

postgresql

• [postgresql] [bug]

  Fixed issue in PostgreSQL ExcludeConstraint where literal values were being compiled as bound parameters and not direct inline values as is required for DDL.

  References: #9349

• [postgresql] [bug]

  Fixed issue where the PostgreSQL ExcludeConstraint construct would not be copyable within operations such as Table.to_metadata() as well as within some Alembic scenarios, if the constraint contained textual expression elements.

  References: #9401

mysql

• [mysql] [bug] [postgresql]

  The support for pool ping listeners to receive exception events via the DialectEvents.handle_error() event added in 2.0.0b1 for #5648 failed to take into account dialect-specific ping routines such as that of MySQL and PostgreSQL. The dialect feature has been reworked so that all dialects participate within event handling. Additionally, a new boolean element ExceptionContext.is_pre_ping is added which identifies if this operation is occurring within the pre-ping operation.

  For this release, third party dialects which implement a custom Dialect.do_ping() method can opt in to the newly improved behavior by having their method no longer catch exceptions or check exceptions for “is_disconnect”, instead just propagating all exceptions outwards. Checking the exception for “is_disconnect” is now done by an enclosing method on the default dialect, which ensures that the event hook is invoked for all exception scenarios before testing the exception as a “disconnect” exception. If an existing do_ping() method continues to catch exceptions and check “is_disconnect”, it will continue to work as it did previously, but handle_error hooks will not have access to the exception if it isn’t propagated outwards.

  References: #5648

sqlite

• [sqlite] [bug] [regression]

  Fixed regression for SQLite connections where use of the deterministic parameter when establishing database functions would fail for older SQLite versions, those prior to version 3.8.3. The version checking logic has been improved to accommodate for this case.

  References: #9379

mssql

• [mssql] [bug]

  Fixed issue in the new Uuid datatype which prevented it from working with the pymssql driver. As pymssql seems to be maintained again, restored testing support for pymssql.

  References: #9414

• [mssql] [bug]

  Tweaked the pymssql dialect to take better advantage of RETURNING for INSERT statements in order to retrieve last inserted primary key values, in the same way as occurs for the mssql+pyodbc dialect right now.

misc

• [bug] [ext]

  Fixed issue in automap where calling AutomapBase.prepare() from a specific mapped class, rather than from the AutomapBase directly, would not use the correct base class when automap detected new tables, instead using the given class, leading to mappers trying to configure inheritance. While one should normally call AutomapBase.prepare() from the base in any case, it shouldn’t misbehave that badly when called from a subclass.

  References: #9367

• [bug] [ext] [regression]

  Fixed regression caused by typing added to sqlalchemy.ext.mutable for #8667, where the semantics of the .pop() method changed such that the method was non-working. Pull request courtesy Nils Philippsen.

  References: #9380

2.0.4

Released: February 17, 2023

orm

• [orm] [usecase]

  To accommodate a change in column ordering used by ORM Declarative in SQLAlchemy 2.0, a new parameter mapped_column.sort_order has been added that can be used to control the order of the columns defined in the table by the ORM, for common use cases such as mixins with primary key columns that should appear first in tables. The change notes at ORM Declarative Applies Column Orders Differently; Control behavior using sort_order illustrate the default change in ordering behavior (which is part of all SQLAlchemy 2.0 releases) as well as use of the mapped_column.sort_order to control column ordering when using mixins and multiple classes (new in 2.0.4).

  See also

  ORM Declarative Applies Column Orders Differently; Control behavior using sort_order

  References: #9297

• [orm] [usecase]

  The Session.refresh() method will now immediately load a relationship-bound attribute that is explicitly named within the Session.refresh.attribute_names collection even if it is currently linked to the “select” loader, which normally is a “lazy” loader that does not fire off during a refresh. The “lazy loader” strategy will now detect that the operation is specifically a user-initiated Session.refresh() operation which named this attribute explicitly, and will then call upon the “immediateload” strategy to actually emit SQL to load the attribute. This should be helpful in particular for some asyncio situations where the loading of an unloaded lazy-loaded attribute must be forced, without using the actual lazy-loading attribute pattern not supported in asyncio.

  References: #9298

• [orm] [bug] [regression]

  Fixed regression introduced in version 2.0.2 due to #9217 where using DML RETURNING statements, as well as Select.from_statement() constructs as was “fixed” in #9217, in conjunction with ORM mapped classes that used expressions such as with column_property(), would lead to an internal error within Core where it would attempt to match the expression by name. The fix repairs the Core issue, and also adjusts the fix in #9217 to not take effect for the DML RETURNING use case, where it adds unnecessary overhead.

  References: #9273

• [orm] [bug]

  Marked the internal EvaluatorCompiler module as private to the ORM, and renamed it to _EvaluatorCompiler. For users that may have been relying upon this, the name EvaluatorCompiler is still present, however this use is not supported and will be removed in a future release.

orm declarative

• [usecase] [orm declarative]

  Added new parameter dataclasses_callable to both the MappedAsDataclass class as well as the registry.mapped_as_dataclass() method which allows an alternative callable to Python dataclasses.dataclass to be used in order to produce dataclasses. The use case here is to drop in Pydantic’s dataclass function instead. Adjustments have been made to the mixin support added for #9179 in version 2.0.1 so that the __annotations__ collection of the mixin is rewritten to not include the Mapped container, in the same way as occurs with mapped classes, so that the Pydantic dataclasses constructor is not exposed to unknown types.

  See also

  Integrating with Alternate Dataclass Providers such as Pydantic

  References: #9266

sql

• [sql] [bug]

  Fixed issue where element types of a tuple value would be hardcoded to take on the types from a compared-to tuple, when the comparison were using the ColumnOperators.in_() operator. This was inconsistent with the usual way that types are determined for a binary expression, which is that the actual element type on the right side is considered first before applying the left-hand-side type.

  References: #9313

• [sql]

  Added public property Table.autoincrement_column that returns the column identified as autoincrementing in the column.

  References: #9277

typing

• [typing] [usecase]

  Improved the typing support for the Hybrid Attributes extension, updated all documentation to use ORM Annotated Declarative mappings, and added a new modifier called hybrid_property.inplace. This modifier provides a way to alter the state of a hybrid_property in place, which is essentially what very early versions of hybrids did, before SQLAlchemy version 1.2.0 #3912 changed this to remove in-place mutation. This in-place mutation is now restored on an opt-in basis to allow a single hybrid to have multiple methods set up, without the need to name all the methods the same and without the need to carefully “chain” differently-named methods in order to maintain the composition. Typing tools such as Mypy and Pyright do not allow same-named methods on a class, so with this change a succinct method of setting up hybrids with typing support is restored.

  See also

  Using inplace to create pep-484 compliant hybrid properties

  References: #9321

oracle

• [oracle] [bug]

  Adjusted the behavior of the thick_mode parameter for the python-oracledb dialect to correctly accept False as a value. Previously, only None would indicate that thick mode should be disabled.

  References: #9295

2.0.3

Released: February 9, 2023

sql

• [sql] [bug] [regression]

  Fixed critical regression in SQL expression formulation in the 2.0 series due to #7744 which improved support for SQL expressions that contained many elements against the same operator repeatedly; parenthesis grouping would be lost with expression elements beyond the first two elements.

  References: #9271

typing

• [typing] [bug]

  Remove typing.Self workaround, now using PEP 673 for most methods that return Self. As a consequence of this change mypy>=1.0.0 is now required to type check SQLAlchemy code. Pull request courtesy Yurii Karabas.

  References: #9254

2.0.2

Released: February 6, 2023

orm

• [orm] [usecase]

  Added new event hook MapperEvents.after_mapper_constructed(), which supplies an event hook to take place right as the Mapper object has been fully constructed, but before the registry.configure() call has been called. This allows code that can create additional mappings and table structures based on the initial configuration of a Mapper, which also integrates within Declarative configuration. Previously, when using Declarative, where the Mapper object is created within the class creation process, there was no documented means of running code at this point. The change is to immediately benefit custom mapping schemes such as that of the Versioning with a History Table example, which generate additional mappers and tables in response to the creation of mapped classes.

  References: #9220

• [orm] [usecase]

  The infrequently used Mapper.iterate_properties attribute and Mapper.get_property() method, which are primarily used internally, no longer implicitly invoke the registry.configure() process. Public access to these methods is extremely rare and the only benefit to having registry.configure() would have been allowing “backref” properties be present in these collections. In order to support the new MapperEvents.after_mapper_constructed() event, iteration and access to the internal MapperProperty objects is now possible without triggering an implicit configure of the mapper itself.

  The more-public facing route to iteration of all mapper attributes, the Mapper.attrs collection and similar, will still implicitly invoke the registry.configure() step thus making backref attributes available.

  In all cases, the registry.configure() is always available to be called directly.

  References: #9220

• [orm] [bug] [ression]

  Fixed obscure ORM inheritance issue caused by #8705 where some scenarios of inheriting mappers that indicated groups of columns from the local table and the inheriting table together under a column_property() would nonetheless warn that properties of the same name were being combined implicitly.

  References: #9232

• [orm] [bug] [regression]

  Fixed regression where using the Mapper.version_id_col feature with a regular Python-side incrementing column would fail to work for SQLite and other databases that don’t support “rowcount” with “RETURNING”, as “RETURNING” would be assumed for such columns even though that’s not what actually takes place.

  References: #9228

• [orm] [bug] [regression]

  Fixed regression when using Select.from_statement() in an ORM context, where matching of columns to SQL labels based on name alone was disabled for ORM-statements that weren’t fully textual. This would prevent arbitrary SQL expressions with column-name labels from matching up to the entity to be loaded, which previously would work within the 1.4 and previous series, so the previous behavior has been restored.

  References: #9217

orm declarative

• [bug] [orm declarative]

  Fixed regression caused by the fix for #9171, which itself was fixing a regression, involving the mechanics of __init__() on classes that extend from DeclarativeBase. The change made it such that __init__() was applied to the user-defined base if there were no __init__() method directly on the class. This has been adjusted so that __init__() is applied only if no other class in the hierarchy of the user-defined base has an __init__() method. This again allows user-defined base classes based on DeclarativeBase to include mixins that themselves include a custom __init__() method.

  References: #9249

• [bug] [orm declarative]

  Fixed issue in ORM Declarative Dataclass mappings related to newly added support for mixins added in 2.0.1 via #9179, where a combination of using mixins plus ORM inheritance would mis-classify fields in some cases leading to field-level dataclass arguments such as init=False being lost.

  References: #9226

• [bug] [orm declarative]

  Repaired ORM Declarative mappings to allow for the Mapper.primary_key parameter to be specified within __mapper_args__ when using mapped_column(). Despite this usage being directly in the 2.0 documentation, the Mapper was not accepting the mapped_column() construct in this context. Ths feature was already working for the Mapper.version_id_col and Mapper.polymorphic_on parameters.

  As part of this change, the __mapper_args__ attribute may be specified without using declared_attr() on a non-mapped mixin class, including a "primary_key" entry that refers to Column or mapped_column() objects locally present on the mixin; Declarative will also translate these columns into the correct ones for a particular mapped class. This again was working already for the Mapper.version_id_col and Mapper.polymorphic_on parameters. Additionally, elements within "primary_key" may be indicated as string names of existing mapped properties.

  References: #9240

• [bug] [orm declarative]

  An explicit error is raised if a mapping attempts to mix the use of MappedAsDataclass with registry.mapped_as_dataclass() within the same class hierarchy, as this produces issues with the dataclass function being applied at the wrong time to the mapped class, leading to errors during the mapping process.

  References: #9211

examples

• [examples] [bug]

  Reworked the Versioning with a History Table to work with version 2.0, while at the same time improving the overall working of this example to use newer APIs, including a newly added hook MapperEvents.after_mapper_constructed().

  References: #9220

sql

• [sql] [usecase]

  Added a full suite of new SQL bitwise operators, for performing database-side bitwise expressions on appropriate data values such as integers, bit-strings, and similar. Pull request courtesy Yegor Statkevich.

  See also

  Bitwise Operators

  References: #8780

asyncio

• [asyncio] [bug]

  Repaired a regression caused by the fix for #8419 which caused asyncpg connections to be reset (i.e. transaction rollback() called) and returned to the pool normally in the case that the connection were not explicitly returned to the connection pool and was instead being intercepted by Python garbage collection, which would fail if the garbage collection operation were being called outside of the asyncio event loop, leading to a large amount of stack trace activity dumped into logging and standard output.

  The correct behavior is restored, which is that all asyncio connections that are garbage collected due to not being explicitly returned to the connection pool are detached from the pool and discarded, along with a warning, rather than being returned the pool, as they cannot be reliably reset. In the case of asyncpg connections, the asyncpg-specific terminate() method will be used to end the connection more gracefully within this process as opposed to just dropping it.

  This change includes a small behavioral change that is hoped to be useful for debugging asyncio applications, where the warning that’s emitted in the case of asyncio connections being unexpectedly garbage collected has been made slightly more aggressive by moving it outside of a try/except block and into a finally: block, where it will emit unconditionally regardless of whether the detach/termination operation succeeded or not. It will also have the effect that applications or test suites which promote Python warnings to exceptions will see this as a full exception raise, whereas previously it was not possible for this warning to actually propagate as an exception. Applications and test suites which need to tolerate this warning in the interim should adjust the Python warnings filter to allow these warnings to not raise.

  The behavior for traditional sync connections remains unchanged, that garbage collected connections continue to be returned to the pool normally without emitting a warning. This will likely be changed in a future major release to at least emit a similar warning as is emitted for asyncio drivers, as it is a usage error for pooled connections to be intercepted by garbage collection without being properly returned to the pool.

  References: #9237

mysql

• [mysql] [bug] [regression]

  Fixed regression caused by issue #9058 which adjusted the MySQL dialect’s has_table() to again use “DESCRIBE”, where the specific error code raised by MySQL version 8 when using a non-existent schema name was unexpected and failed to be interpreted as a boolean result.

  References: #9251

• [mysql] [bug]

  Added support for MySQL 8’s new AS <name> ON DUPLICATE KEY syntax when using Insert.on_duplicate_key_update(), which is required for newer versions of MySQL 8 as the previous syntax using VALUES() now emits a deprecation warning with those versions. Server version detection is employed to determine if traditional MariaDB / MySQL < 8 VALUES() syntax should be used, vs. the newer MySQL 8 required syntax. Pull request courtesy Caspar Wylie.

  References: #8626

sqlite

• [sqlite] [bug]

  Fixed the SQLite dialect’s has_table() function to correctly report False for queries that include a non-None schema name for a schema that doesn’t exist; previously, a database error was raised.

  References: #9251

2.0.1

Released: February 1, 2023

orm

• [orm] [bug] [regression]

  Fixed regression where ORM models that used joined table inheritance with a composite foreign key would encounter an internal error in the mapper internals.

  References: #9164

• [orm] [bug]

  Improved the error reporting when linking strategy options from a base class to another attribute that’s off a subclass, where of_type() should be used. Previously, when Load.options() is used, the message would lack informative detail that of_type() should be used, which was not the case when linking the options directly. The informative detail now emits even if Load.options() is used.

  References: #9182

orm declarative

• [bug] [orm declarative]

  Added support for PEP 484 NewType to be used in the registry.type_annotation_map as well as within Mapped constructs. These types will behave in the same way as custom subclasses of types right now; they must appear explicitly within the registry.type_annotation_map to be mapped.

  References: #9175

• [bug] [orm declarative]

  When using the MappedAsDataclass superclass, all classes within the hierarchy that are subclasses of this class will now be run through the @dataclasses.dataclass function whether or not they are actually mapped, so that non-ORM fields declared on non-mapped classes within the hierarchy will be used when mapped subclasses are turned into dataclasses. This behavior applies both to intermediary classes mapped with __abstract__ = True as well as to the user-defined declarative base itself, assuming MappedAsDataclass is present as a superclass for these classes.

  This allows non-mapped attributes such as InitVar declarations on superclasses to be used, without the need to run the @dataclasses.dataclass decorator explicitly on each non-mapped class. The new behavior is considered as correct as this is what the PEP 681 implementation expects when using a superclass to indicate dataclass behavior.

  References: #9179

• [bug] [orm declarative]

  Added support for PEP 586 Literal[] to be used in the registry.type_annotation_map as well as within Mapped constructs. To use custom types such as these, they must appear explicitly within the registry.type_annotation_map to be mapped. Pull request courtesy Frederik Aalund.

  As part of this change, the support for Enum in the registry.type_annotation_map has been expanded to include support for Literal[] types consisting of string values to be used, in addition to enum.Enum datatypes. If a Literal[] datatype is used within Mapped[] that is not linked in registry.type_annotation_map to a specific datatype, a Enum will be used by default.

  See also

  Using Python Enum or pep-586 Literal types in the type map

  References: #9187

• [bug] [orm declarative]

  Fixed issue involving the use of Enum within the registry.type_annotation_map where the Enum.native_enum parameter would not be correctly copied to the mapped column datatype, if it were overridden as stated in the documentation to set this parameter to False.

  References: #9200

• [bug] [orm declarative] [regression]

  Fixed regression in DeclarativeBase class where the registry’s default constructor would not be applied to the base itself, which is different from how the previous declarative_base() construct works. This would prevent a mapped class with its own __init__() method from calling super().__init__() in order to access the registry’s default constructor and automatically populate attributes, instead hitting object.__init__() which would raise a TypeError on any arguments.

  References: #9171

• [bug] [orm declarative]

  Improved the ruleset used to interpret PEP 593 Annotated types when used with Annotated Declarative mapping, the inner type will be checked for “Optional” in all cases which will be added to the criteria by which the column is set as “nullable” or not; if the type within the Annotated container is optional (or unioned with None), the column will be considered nullable if there are no explicit mapped_column.nullable parameters overriding it.

  References: #9177

sql

• [sql] [bug]

  Corrected the fix for #7664, released in version 2.0.0, to also include DropSchema which was inadvertently missed in this fix, allowing stringification without a dialect. The fixes for both constructs is backported to the 1.4 series as of 1.4.47.

  References: #7664

• [sql] [bug] [regression]

  Fixed regression related to the implementation for the new “insertmanyvalues” feature where an internal TypeError would occur in arrangements where a insert() would be referenced inside of another insert() via a CTE; made additional repairs for this use case for positional dialects such as asyncpg when using “insertmanyvalues”.

  References: #9173

typing

• [typing] [bug]

  Opened up typing on Select.with_for_update.of to also accept table and mapped class arguments, as seems to be available for the MySQL dialect.

  References: #9174

• [typing] [bug]

  Fixed typing for limit/offset methods including Select.limit(), Select.offset(), Query.limit(), Query.offset() to allow None, which is the documented API to “cancel” the current limit/offset.

  References: #9183

• [typing] [bug]

  Fixed typing issue where mapped_column() objects typed as Mapped wouldn’t be accepted in schema constraints such as ForeignKey, UniqueConstraint or Index.

  References: #9170

• [typing] [bug]

  Fixed typing for ColumnElement.cast() to accept both Type[TypeEngine[T]] and TypeEngine[T]; previously only TypeEngine[T] was accepted. Pull request courtesy Yurii Karabas.

  References: #9156

2.0.0

Released: January 26, 2023

orm

• [orm] [bug]

  Improved the notification of warnings that are emitted within the configure mappers or flush process, which are often invoked as part of a different operation, to add additional context to the message that indicates one of these operations as the source of the warning within operations that may not be obviously related.

  References: #7305

orm extensions

• [feature] [orm extensions]

  Added new option to horizontal sharding API set_shard_id which sets the effective shard identifier to query against, for both the primary query as well as for all secondary loaders including relationship eager loaders as well as relationship and column lazy loaders.

  References: #7226

• [usecase] [orm extensions]

  Added new feature to AutomapBase for autoload of classes across multiple schemas which may have overlapping names, by providing a AutomapBase.prepare.modulename_for_table parameter which allows customization of the __module__ attribute of newly generated classes, as well as a new collection AutomapBase.by_module, which stores a dot-separated namespace of module names linked to classes based on the __module__ attribute.

  Additionally, the AutomapBase.prepare() method may now be invoked any number of times, with or without reflection enabled; only newly added tables that were not previously mapped will be processed on each call. Previously, the MetaData.reflect() method would need to be called explicitly each time.

  See also

  Generating Mappings from Multiple Schemas - illustrates use of both techniques at once.

  References: #5145

sql

• [sql] [bug]

  Fixed stringify for a the CreateSchema DDL construct, which would fail with an AttributeError when stringified without a dialect. Update: Note this fix failed to accommodate for DropSchema; a followup fix in version 2.0.1 repairs this case. The fix for both elements is backported to 1.4.47.

  References: #7664

typing

• [typing] [bug]

  Added typing for the built-in generic functions that are available from the func namespace, which accept a particular set of arguments and return a particular type, such as for count, current_timestamp, etc.

  References: #9129

• [typing] [bug]

  Corrected the type passed for “lambda statements” so that a plain lambda is accepted by mypy, pyright, others without any errors about argument types. Additionally implemented typing for more of the public API for lambda statements and ensured StatementLambdaElement is part of the Executable hierarchy so it’s typed as accepted by Connection.execute().

  References: #9120

• [typing] [bug]

  The ColumnOperators.in_() and ColumnOperators.not_in() methods are typed to include Iterable[Any] rather than Sequence[Any] for more flexibility in argument type.

  References: #9122

• [typing] [bug]

  The or_() and and_() from a typing perspective require the first argument to be present, however these functions still accept zero arguments which will emit a deprecation warning at runtime. Typing is also added to support sending the fixed literal False for or_() and True for and_() as the first argument only, however the documentation now indicates sending the false() and true() constructs in these cases as a more explicit approach.

  References: #9123

• [typing] [bug]

  Fixed typing issue where iterating over a Query object was not correctly typed.

  References: #9125

• [typing] [bug]

  Fixed typing issue where the object type when using Result as a context manager were not preserved, indicating Result in all cases rather than the specific Result sub-type. Pull request courtesy Martin Baláž.

  References: #9136

• [typing] [bug]

  Fixed issue where using the relationship.remote_side and similar parameters, passing an annotated declarative object typed as Mapped, would not be accepted by the type checker.

  References: #9150

• [typing] [bug]

  Added typing to legacy operators such as isnot(), notin_(), etc. which previously were referencing the newer operators but were not themselves typed.

  References: #9148

postgresql

• [postgresql] [bug]

  Added support to the asyncpg dialect to return the cursor.rowcount value for SELECT statements when available. While this is not a typical use for cursor.rowcount, the other PostgreSQL dialects generally provide this value. Pull request courtesy Michael Gorven.

  This change is also backported to: 1.4.47

  References: #9048

mysql

• [mysql] [usecase]

  Added support to MySQL index reflection to correctly reflect the mysql_length dictionary, which previously was being ignored.

  This change is also backported to: 1.4.47

  References: #9047

mssql

• [mssql] [bug] [regression]

  The newly added comment reflection and rendering capability of the MSSQL dialect, added in #7844, will now be disabled by default if it cannot be determined that an unsupported backend such as Azure Synapse may be in use; this backend does not support table and column comments and does not support the SQL Server routines in use to generate them as well as to reflect them. A new parameter supports_comments is added to the dialect which defaults to None, indicating that comment support should be auto-detected. When set to True or False, the comment support is either enabled or disabled unconditionally.

  See also

  DDL Comment Support

  References: #9142

2.0.0rc3

Released: January 18, 2023

orm

• [orm] [feature]

  Added a new parameter to Mapper called Mapper.polymorphic_abstract. The purpose of this directive is so that the ORM will not consider the class to be instantiated or loaded directly, only subclasses. The actual effect is that the Mapper will prevent direct instantiation of instances of the class and will expect that the class does not have a distinct polymorphic identity configured.

  In practice, the class that is mapped with Mapper.polymorphic_abstract can be used as the target of a relationship() as well as be used in queries; subclasses must of course include polymorphic identities in their mappings.

  The new parameter is automatically applied to classes that subclass the AbstractConcreteBase class, as this class is not intended to be instantiated.

  See also

  Building Deeper Hierarchies with polymorphic_abstract

  References: #9060

• [orm] [bug]

  Fixed issue where using a pep-593 Annotated type in the registry.type_annotation_map which itself contained a generic plain container or collections.abc type (e.g. list, dict, collections.abc.Sequence, etc. ) as the target type would produce an internal error when the ORM were trying to interpret the Annotated instance.

  References: #9099

• [orm] [bug]

  Added an error message when a relationship() is mapped against an abstract container type, such as Mapped[Sequence[B]], without providing the relationship.container_class parameter which is necessary when the type is abstract. Previously the the abstract container would attempt to be instantiated at a later step and fail.

  References: #9100

sql

• [sql] [bug]

  Fixed bug / regression where using bindparam() with the same name as a column in the Update.values() method of Update, as well as the Insert.values() method of Insert in 2.0 only, would in some cases silently fail to honor the SQL expression in which the parameter were presented, replacing the expression with a new parameter of the same name and discarding any other elements of the SQL expression, such as SQL functions, etc. The specific case would be statements that were constructed against ORM entities rather than plain Table instances, but would occur if the statement were invoked with a Session or a Connection.

  Update part of the issue was present in both 2.0 and 1.4 and is backported to 1.4.

  This change is also backported to: 1.4.47

  References: #9075

typing

• [typing] [bug]

  Fixes to the annotations within the sqlalchemy.ext.hybrid extension for more effective typing of user-defined methods. The typing now uses PEP 612 features, now supported by recent versions of Mypy, to maintain argument signatures for hybrid_method. Return values for hybrid methods are accepted as SQL expressions in contexts such as Select.where() while still supporting SQL methods.

  References: #9096

mypy

• [mypy] [bug]

  Adjustments made to the mypy plugin to accommodate for some potential changes being made for issue #236 sqlalchemy2-stubs when using SQLAlchemy 1.4. These changes are being kept in sync within SQLAlchemy 2.0. The changes are also backwards compatible with older versions of sqlalchemy2-stubs.

  This change is also backported to: 1.4.47

• [mypy] [bug]

  Fixed crash in mypy plugin which could occur on both 1.4 and 2.0 versions if a decorator for the mapped() decorator were used that was referenced in an expression with more than two components (e.g. @Backend.mapper_registry.mapped). This scenario is now ignored; when using the plugin, the decorator expression needs to be two components (i.e. @reg.mapped).

  This change is also backported to: 1.4.47

  References: #9102

postgresql

• [postgresql] [bug]

  Fixed regression where psycopg3 changed an API call as of version 3.1.8 to expect a specific object type that was previously not enforced, breaking connectivity for the psycopg3 dialect.

  References: #9106

oracle

• [oracle] [usecase]

  Added support for the Oracle SQL type TIMESTAMP WITH LOCAL TIME ZONE, using a newly added Oracle-specific TIMESTAMP datatype.

  References: #9086

2.0.0rc2

Released: January 9, 2023

orm

• [orm] [bug]

  Fixed issue where an overly restrictive ORM mapping rule were added in 2.0 which prevented mappings against TableClause objects, such as those used in the view recipe on the wiki.

  References: #9071

typing

• [typing] [bug]

  The Data Class Transforms argument field_descriptors was renamed to field_specifiers in the accepted version of PEP 681.

  References: #9067

postgresql

• [postgresql] [json]

  Implemented missing JSONB operations:

  • @@ using Comparator.path_match()

  • @? using Comparator.path_exists()

  • #- using Comparator.delete_path()

  Pull request courtesy of Guilherme Martins Crocetti.

  References: #7147

mysql

• [mysql] [bug]

  Restored the behavior of Inspector.has_table() to report on temporary tables for MySQL / MariaDB. This is currently the behavior for all other included dialects, but was removed for MySQL in 1.4 due to no longer using the DESCRIBE command; there was no documented support for temp tables being reported by the Inspector.has_table() method in this version or on any previous version, so the previous behavior was undefined.

  As SQLAlchemy 2.0 has added formal support for temp table status via Inspector.has_table(), the MySQL /MariaDB dialect has been reverted to use the “DESCRIBE” statement as it did in the SQLAlchemy 1.3 series and previously, and test support is added to include MySQL / MariaDB for this behavior. The previous issues with ROLLBACK being emitted which 1.4 sought to improve upon don’t apply in SQLAlchemy 2.0 due to simplifications in how Connection handles transactions.

  DESCRIBE is necessary as MariaDB in particular has no consistently available public information schema of any kind in order to report on temp tables other than DESCRIBE/SHOW COLUMNS, which rely on throwing an error in order to report no results.

  References: #9058

oracle

• [oracle] [bug]

  Supported use case for foreign key constraints where the local column is marked as “invisible”. The errors normally generated when a ForeignKeyConstraint is created that check for the target column are disabled when reflecting, and the constraint is skipped with a warning in the same way which already occurs for an Index with a similar issue.

  References: #9059

2.0.0rc1

Released: December 28, 2022

general

• [general] [bug]

  Fixed regression where the base compat module was calling upon platform.architecture() in order to detect some system properties, which results in an over-broad system call against the system-level file call that is unavailable under some circumstances, including within some secure environment configurations.

  This change is also backported to: 1.4.46

  References: #8995

orm

• [orm] [feature]

  Added a new default value for the Mapper.eager_defaults parameter “auto”, which will automatically fetch table default values during a unit of work flush, if the dialect supports RETURNING for the INSERT being run, as well as insertmanyvalues available. Eager fetches for server-side UPDATE defaults, which are very uncommon, continue to only take place if Mapper.eager_defaults is set to True, as there is no batch-RETURNING form for UPDATE statements.

  References: #8889

• [orm] [usecase]

  Adjustments to the Session in terms of extensibility, as well as updates to the ShardedSession extension:

  • Session.get() now accepts Session.get.bind_arguments, which in particular may be useful when using the horizontal sharding extension.

  • Session.get_bind() accepts arbitrary kw arguments, which assists in developing code that uses a Session class which overrides this method with additional arguments.

  • Added a new ORM execution option identity_token which may be used to directly affect the “identity token” that will be associated with newly loaded ORM objects. This token is how sharding approaches (namely the ShardedSession, but can be used in other cases as well) separate object identities across different “shards”.

    See also

    Identity Token

  • The SessionEvents.do_orm_execute() event hook may now be used to affect all ORM-related options, including autoflush, populate_existing, and yield_per; these options are re-consumed subsequent to event hooks being invoked before they are acted upon. Previously, options like autoflush would have been already evaluated at this point. The new identity_token option is also supported in this mode and is now used by the horizontal sharding extension.

  • The ShardedSession class replaces the ShardedSession.id_chooser hook with a new hook ShardedSession.identity_chooser, which no longer relies upon the legacy Query object. ShardedSession.id_chooser is still accepted in place of ShardedSession.identity_chooser with a deprecation warning.

  References: #7837

• [orm] [usecase]

  The behavior of “joining an external transaction into a Session” has been revised and improved, allowing explicit control over how the Session will accommodate an incoming Connection that already has a transaction and possibly a savepoint already established. The new parameter Session.join_transaction_mode includes a series of option values which can accommodate the existing transaction in several ways, most importantly allowing a Session to operate in a fully transactional style using savepoints exclusively, while leaving the externally initiated transaction non-committed and active under all circumstances, allowing test suites to rollback all changes that take place within tests.

  Additionally, revised the Session.close() method to fully close out savepoints that may still be present, which also allows the “external transaction” recipe to proceed without warnings if the Session did not explicitly end its own SAVEPOINT transactions.

  See also

  New transaction join modes for Session

  References: #9015

• [orm] [usecase]

  Removed the requirement that the __allow_unmapped__ attribute be used on Declarative Dataclass Mapped class when non-Mapped[] annotations are detected; previously, an error message that was intended to support legacy ORM typed mappings would be raised, which additionally did not mention correct patterns to use with Dataclasses specifically. This error message is now no longer raised if registry.mapped_as_dataclass() or MappedAsDataclass is used.

  See also

  Using Non-Mapped Dataclass Fields

  References: #8973

• [orm] [bug]

  Fixed issue in the internal SQL traversal for DML statements like Update and Delete which would cause among other potential issues, a specific issue using lambda statements with the ORM update/delete feature.

  This change is also backported to: 1.4.46

  References: #9033

• [orm] [bug]

  Fixed bug where Session.merge() would fail to preserve the current loaded contents of relationship attributes that were indicated with the relationship.viewonly parameter, thus defeating strategies that use Session.merge() to pull fully loaded objects from caches and other similar techniques. In a related change, fixed issue where an object that contains a loaded relationship that was nonetheless configured as lazy='raise' on the mapping would fail when passed to Session.merge(); checks for “raise” are now suspended within the merge process assuming the Session.merge.load parameter remains at its default of True.

  Overall, this is a behavioral adjustment to a change introduced in the 1.4 series as of #4994, which took “merge” out of the set of cascades applied by default to “viewonly” relationships. As “viewonly” relationships aren’t persisted under any circumstances, allowing their contents to transfer during “merge” does not impact the persistence behavior of the target object. This allows Session.merge() to correctly suit one of its use cases, that of adding objects to a Session that were loaded elsewhere, often for the purposes of restoring from a cache.

  This change is also backported to: 1.4.45

  References: #8862

• [orm] [bug]

  Fixed issues in with_expression() where expressions that were composed of columns that were referenced from the enclosing SELECT would not render correct SQL in some contexts, in the case where the expression had a label name that matched the attribute which used query_expression(), even when query_expression() had no default expression. For the moment, if the query_expression() does have a default expression, that label name is still used for that default, and an additional label with the same name will continue to be ignored. Overall, this case is pretty thorny so further adjustments might be warranted.

  This change is also backported to: 1.4.45

  References: #8881

• [orm] [bug]

  A warning is emitted if a backref name used in relationship() names an attribute on the target class which already has a method or attribute assigned to that name, as the backref declaration will replace that attribute.

  References: #4629

• [orm] [bug]

  A series of changes and improvements regarding Session.refresh(). The overall change is that primary key attributes for an object are now included in a refresh operation unconditionally when relationship-bound attributes are to be refreshed, even if not expired and even if not specified in the refresh.

  • Improved Session.refresh() so that if autoflush is enabled (as is the default for Session), the autoflush takes place at an earlier part of the refresh process so that pending primary key changes are applied without errors being raised. Previously, this autoflush took place too late in the process and the SELECT statement would not use the correct key to locate the row and an InvalidRequestError would be raised.

  • When the above condition is present, that is, unflushed primary key changes are present on the object, but autoflush is not enabled, the refresh() method now explicitly disallows the operation to proceed, and an informative InvalidRequestError is raised asking that the pending primary key changes be flushed first. Previously, this use case was simply broken and InvalidRequestError would be raised anyway. This restriction is so that it’s safe for the primary key attributes to be refreshed, as is necessary for the case of being able to refresh the object with relationship-bound secondary eagerloaders also being emitted. This rule applies in all cases to keep API behavior consistent regardless of whether or not the PK cols are actually needed in the refresh, as it is unusual to be refreshing some attributes on an object while keeping other attributes “pending” in any case.

  • The Session.refresh() method has been enhanced such that attributes which are relationship()-bound and linked to an eager loader, either at mapping time or via last-used loader options, will be refreshed in all cases even when a list of attributes is passed that does not include any columns on the parent row. This builds upon the feature first implemented for non-column attributes as part of #1763 fixed in 1.4 allowing eagerly-loaded relationship-bound attributes to participate in the Session.refresh() operation. If the refresh operation does not indicate any columns on the parent row to be refreshed, the primary key columns will nonetheless be included in the refresh operation, which allows the load to proceed into the secondary relationship loaders indicated as it does normally. Previously an InvalidRequestError error would be raised for this condition (#8703)

  • Fixed issue where an unnecessary additional SELECT would be emitted in the case where Session.refresh() were called with a combination of expired attributes, as well as an eager loader such as selectinload() that emits a “secondary” query, if the primary key attributes were also in an expired state. As the primary key attributes are now included in the refresh automatically, there is no additional load for these attributes when a relationship loader goes to select for them (#8997)

  • Fixed regression caused by #8126 released in 2.0.0b1 where the Session.refresh() method would fail with an AttributeError, if passed both an expired column name as well as the name of a relationship-bound attribute that was linked to a “secondary” eagerloader such as the selectinload() eager loader (#8996)

  References: #8703, #8996, #8997

• [orm] [bug]

  Improved a fix first made in version 1.4 for #8456 which scaled back the usage of internal “polymorphic adapters”, that are used to render ORM queries when the Mapper.with_polymorphic parameter is used. These adapters, which are very complex and error prone, are now used only in those cases where an explicit user-supplied subquery is used for Mapper.with_polymorphic, which includes only the use case of concrete inheritance mappings that use the polymorphic_union() helper, as well as the legacy use case of using an aliased subquery for joined inheritance mappings, which is not needed in modern use.

  For the most common case of joined inheritance mappings that use the built-in polymorphic loading scheme, which includes those which make use of the Mapper.polymorphic_load parameter set to inline, polymorphic adapters are now no longer used. This has both a positive performance impact on the construction of queries as well as a substantial simplification of the internal query rendering process.

  The specific issue targeted was to allow a column_property() to refer to joined-inheritance classes within a scalar subquery, which now works as intuitively as is feasible.

  References: #8168

engine

• [engine] [bug]

  Fixed a long-standing race condition in the connection pool which could occur under eventlet/gevent monkeypatching schemes in conjunction with the use of eventlet/gevent Timeout conditions, where a connection pool checkout that’s interrupted due to the timeout would fail to clean up the failed state, causing the underlying connection record and sometimes the database connection itself to “leak”, leaving the pool in an invalid state with unreachable entries. This issue was first identified and fixed in SQLAlchemy 1.2 for #4225, however the failure modes detected in that fix failed to accommodate for BaseException, rather than Exception, which prevented eventlet/gevent Timeout from being caught. In addition, a block within initial pool connect has also been identified and hardened with a BaseException -> “clean failed connect” block to accommodate for the same condition in this location. Big thanks to Github user @niklaus for their tenacious efforts in identifying and describing this intricate issue.

  This change is also backported to: 1.4.46

  References: #8974

• [engine] [bug]

  Fixed issue where Result.freeze() method would not work for textual SQL using either text() or Connection.exec_driver_sql().

  This change is also backported to: 1.4.45

  References: #8963

sql

• [sql] [usecase]

  An informative re-raise is now thrown in the case where any “literal bindparam” render operation fails, indicating the value itself and the datatype in use, to assist in debugging when literal params are being rendered in a statement.

  This change is also backported to: 1.4.45

  References: #8800

• [sql] [bug]

  Fixed issue in lambda SQL feature where the calculated type of a literal value would not take into account the type coercion rules of the “compared to type”, leading to a lack of typing information for SQL expressions, such as comparisons to JSON elements and similar.

  This change is also backported to: 1.4.46

  References: #9029

• [sql] [bug]

  Fixed a series of issues regarding the position and sometimes the identity of rendered bound parameters, such as those used for SQLite, asyncpg, MySQL, Oracle and others. Some compiled forms would not maintain the order of parameters correctly, such as the PostgreSQL regexp_replace() function, the “nesting” feature of the CTE construct first introduced in #4123, and selectable tables formed by using the FunctionElement.column_valued() method with Oracle.

  This change is also backported to: 1.4.45

  References: #8827

• [sql] [bug]

  Added test support to ensure that all compiler visit_xyz() methods across all Compiler implementations in SQLAlchemy accept a **kw parameter, so that all compilers accept additional keyword arguments under all circumstances.

  References: #8988

• [sql] [bug]

  The SQLCompiler.construct_params() method, as well as the SQLCompiler.params accessor, will now return the exact parameters that correspond to a compiled statement that used the render_postcompile parameter to compile. Previously, the method returned a parameter structure that by itself didn’t correspond to either the original parameters or the expanded ones.

  Passing a new dictionary of parameters to SQLCompiler.construct_params() for a SQLCompiler that was constructed with render_postcompile is now disallowed; instead, to make a new SQL string and parameter set for an alternate set of parameters, a new method SQLCompiler.construct_expanded_state() is added which will produce a new expanded form for the given parameter set, using the ExpandedState container which includes a new SQL statement and new parameter dictionary, as well as a positional parameter tuple.

  References: #6114

• [sql] [bug]

  To accommodate for third party dialects with different character escaping needs regarding bound parameters, the system by which SQLAlchemy “escapes” (i.e., replaces with another character in its place) special characters in bound parameter names has been made extensible for third party dialects, using the SQLCompiler.bindname_escape_chars dictionary which can be overridden at the class declaration level on any SQLCompiler subclass. As part of this change, also added the dot "." as a default “escaped” character.

  References: #8994

typing

• [typing] [bug]

  pep-484 typing has been completed for the sqlalchemy.ext.horizontal_shard extension as well as the sqlalchemy.orm.events module. Thanks to Gleb Kisenkov for their efforts.

  References: #6810, #9025

asyncio

• [asyncio] [bug]

  Removed non-functional merge() method from AsyncResult. This method has never worked and was included with AsyncResult in error.

  This change is also backported to: 1.4.45

  References: #8952

postgresql

• [postgresql] [bug]

  Fixed bug where the PostgreSQL Insert.on_conflict_do_update.constraint parameter would accept an Index object, however would not expand this index out into its individual index expressions, instead rendering its name in an ON CONFLICT ON CONSTRAINT clause, which is not accepted by PostgreSQL; the “constraint name” form only accepts unique or exclude constraint names. The parameter continues to accept the index but now expands it out into its component expressions for the render.

  This change is also backported to: 1.4.46

  References: #9023

• [postgresql] [bug]

  Made an adjustment to how the PostgreSQL dialect considers column types when it reflects columns from a table, to accommodate for alternative backends which may return NULL from the PG format_type() function.

  This change is also backported to: 1.4.45

  References: #8748

• [postgresql] [bug]

  Added support for explicit use of PG full text functions with asyncpg and psycopg (SQLAlchemy 2.0 only), with regards to the REGCONFIG type cast for the first argument, which previously would be incorrectly cast to a VARCHAR, causing failures on these dialects that rely upon explicit type casts. This includes support for to_tsvector, to_tsquery, plainto_tsquery, phraseto_tsquery, websearch_to_tsquery, ts_headline, each of which will determine based on number of arguments passed if the first string argument should be interpreted as a PostgreSQL “REGCONFIG” value; if so, the argument is typed using a newly added type object REGCONFIG which is then explicitly cast in the SQL expression.

  References: #8977

• [postgresql] [bug]

  Fixed regression where newly revised PostgreSQL range types such as INT4RANGE could not be set up as the impl of a TypeDecorator custom type, instead raising a TypeError.

  References: #9020

• [postgresql] [bug]

  The Range.__eq___() will now return NotImplemented when comparing with an instance of a different class, instead of raising an AttributeError exception.

  References: #8984

sqlite

• [sqlite] [usecase]

  Added support for the SQLite backend to reflect the “DEFERRABLE” and “INITIALLY” keywords which may be present on a foreign key construct. Pull request courtesy Michael Gorven.

  This change is also backported to: 1.4.45

  References: #8903

• [sqlite] [usecase]

  Added support for reflection of expression-oriented WHERE criteria included in indexes on the SQLite dialect, in a manner similar to that of the PostgreSQL dialect. Pull request courtesy Tobias Pfeiffer.

  This change is also backported to: 1.4.45

  References: #8804

oracle

• [oracle] [bug]

  Fixed issue in Oracle compiler where the syntax for FunctionElement.column_valued() was incorrect, rendering the name COLUMN_VALUE without qualifying the source table correctly.

  This change is also backported to: 1.4.45

  References: #8945

tests

• [tests] [bug]

  Fixed issue in tox.ini file where changes in the tox 4.0 series to the format of “passenv” caused tox to not function correctly, in particular raising an error as of tox 4.0.6.

  This change is also backported to: 1.4.46

• [tests] [bug]

  Added new exclusion rule for third party dialects called unusual_column_name_characters, which can be “closed” for third party dialects that don’t support column names with unusual characters such as dots, slashes, or percent signs in them, even if the name is properly quoted.

  This change is also backported to: 1.4.46

  References: #9002

2.0.0b4

Released: December 5, 2022

orm

• [orm] [feature]

  Added a new parameter mapped_column.use_existing_column to accommodate the use case of a single-table inheritance mapping that uses the pattern of more than one subclass indicating the same column to take place on the superclass. This pattern was previously possible by using declared_attr() in conjunction with locating the existing column in the .__table__ of the superclass, however is now updated to work with mapped_column() as well as with pep-484 typing, in a simple and succinct way.

  See also

  Resolving Column Conflicts with use_existing_column

  References: #8822

• [orm] [usecase]

  Added support custom user-defined types which extend the Python enum.Enum base class to be resolved automatically to SQLAlchemy Enum SQL types, when using the Annotated Declarative Table feature. The feature is made possible through new lookup features added to the ORM type map feature, and includes support for changing the arguments of the Enum that’s generated by default as well as setting up specific enum.Enum types within the map with specific arguments.

  See also

  Using Python Enum or pep-586 Literal types in the type map

  References: #8859

• [orm] [usecase]

  Added mapped_column.compare parameter to relevant ORM attribute constructs including mapped_column(), relationship() etc. to provide for the Python dataclasses compare parameter on field(), when using the Declarative Dataclass Mapping feature. Pull request courtesy Simon Schiele.

  References: #8905

• [orm] [bug]

  Fixed issue where use of an unknown datatype within a Mapped annotation for a column-based attribute would silently fail to map the attribute, rather than reporting an exception; an informative exception message is now raised.

  References: #8888

• [orm] [bug]

  Fixed a suite of issues involving Mapped use with dictionary types, such as Mapped[Dict[str, str] | None], would not be correctly interpreted in Declarative ORM mappings. Support to correctly “de-optionalize” this type including for lookup in type_annotation_map has been fixed.

  References: #8777

• [orm] [bug] [performance]

  Additional performance enhancements within ORM-enabled SQL statements, specifically targeting callcounts within the construction of ORM statements, using combinations of aliased() with union() and similar “compound” constructs, in addition to direct performance improvements to the corresponding_column() internal method that is used heavily by the ORM by constructs like aliased() and similar.

  References: #8796

• [orm] [bug]

  Fixed bug in Declarative Dataclass Mapping feature where using plain dataclass fields with the __allow_unmapped__ directive in a mapping would not create a dataclass with the correct class-level state for those fields, copying the raw Field object to the class inappropriately after dataclasses itself had replaced the Field object with the class-level default value.

  References: #8880

• [orm] [bug] [regression]

  Fixed regression where flushing a mapped class that’s mapped against a subquery, such as a direct mapping or some forms of concrete table inheritance, would fail if the Mapper.eager_defaults parameter were used.

  References: #8812

• [orm] [bug]

  Fixed regression in 2.0.0b3 caused by #8759 where indicating the Mapped name using a qualified name such as sqlalchemy.orm.Mapped would fail to be recognized by Declarative as indicating the Mapped construct.

  References: #8853

orm extensions

• [usecase] [orm extensions]

  Added support for the association_proxy() extension function to take part within Python dataclasses configuration, when using the native dataclasses feature described at Declarative Dataclass Mapping. Included are attribute-level arguments including association_proxy.init and association_proxy.default_factory.

  Documentation for association proxy has also been updated to use “Annotated Declarative Table” forms within examples, including type annotations used for AssocationProxy itself.

  References: #8878

sql

• [sql] [usecase]

  Added ScalarValues that can be used as a column element allowing using Values inside IN clauses or in conjunction with ANY or ALL collection aggregates. This new class is generated using the method Values.scalar_values(). The Values instance is now coerced to a ScalarValues when used in a IN or NOT IN operation.

  References: #6289

• [sql] [bug]

  Fixed critical memory issue identified in cache key generation, where for very large and complex ORM statements that make use of lots of ORM aliases with subqueries, cache key generation could produce excessively large keys that were orders of magnitude bigger than the statement itself. Much thanks to Rollo Konig Brock for their very patient, long term help in finally identifying this issue.

  This change is also backported to: 1.4.44

  References: #8790

• [sql] [bug]

  The approach to the numeric pep-249 paramstyle has been rewritten, and is now fully supported, including by features such as “expanding IN” and “insertmanyvalues”. Parameter names may also be repeated in the source SQL construct which will be correctly represented within the numeric format using a single parameter. Introduced an additional numeric paramstyle called numeric_dollar, which is specifically what’s used by the asyncpg dialect; the paramstyle is equivalent to numeric except numeric indicators are indicated by a dollar-sign rather than a colon. The asyncpg dialect now uses numeric_dollar paramstyle directly, rather than compiling to format style first.

  The numeric and numeric_dollar paramstyles assume that the target backend is capable of receiving the numeric parameters in any order, and will match the given parameter values to the statement based on matching their position (1-based) to the numeric indicator. This is the normal behavior of “numeric” paramstyles, although it was observed that the SQLite DBAPI implements a not-used “numeric” style that does not honor parameter ordering.

  References: #8849

• [sql] [bug]

  Adjusted the rendering of RETURNING, in particular when using Insert, such that it now renders columns using the same logic as that of the Select construct to generate labels, which will include disambiguating labels, as well as that a SQL function surrounding a named column will be labeled using the column name itself. This establishes better cross-compatibility when selecting rows from either Select constructs or from DML statements that use UpdateBase.returning(). A narrower scale change was also made for the 1.4 series that adjusted the function label issue only.

  References: #8770

schema

• [schema] [bug]

  Stricter rules are in place for appending of Column objects to Table objects, both moving some previous deprecation warnings to exceptions, and preventing some previous scenarios that would cause duplicate columns to appear in tables, when Table.extend_existing were set to True, for both programmatic Table construction as well as during reflection operations.

  See Stricter rules for replacement of Columns in Table objects with same-names, keys for a rundown of these changes.

  See also

  Stricter rules for replacement of Columns in Table objects with same-names, keys

  References: #8925

typing

• [typing] [usecase]

  Added a new type SQLColumnExpression which may be indicated in user code to represent any SQL column oriented expression, including both those based on ColumnElement as well as on ORM QueryableAttribute. This type is a real class, not an alias, so can also be used as the foundation for other objects. An additional ORM-specific subclass SQLORMExpression is also included.

  References: #8847

• [typing] [bug]

  Adjusted internal use of the Python enum.IntFlag class which changed its behavioral contract in Python 3.11. This was not causing runtime failures however caused typing runs to fail under Python 3.11.

  References: #8783

• [typing] [bug]

  The sqlalchemy.ext.mutable extension and sqlalchemy.ext.automap extensions are now fully pep-484 typed. Huge thanks to Gleb Kisenkov for their efforts on this.

  References: #6810, #8667

• [typing] [bug]

  Corrected typing support for the relationship.secondary argument which may also accept a callable (lambda) that returns a FromClause.

• [typing] [bug]

  Improved the typing for sessionmaker and async_sessionmaker, so that the default type of their return value will be Session or AsyncSession, without the need to type this explicitly. Previously, Mypy would not automaticaly infer these return types from its generic base.

  As part of this change, arguments for Session, AsyncSession, sessionmaker and async_sessionmaker beyond the initial “bind” argument have been made keyword-only, which includes parameters that have always been documented as keyword arguments, such as Session.autoflush, Session.class_, etc.

  Pull request courtesy Sam Bull.

  References: #8842

• [typing] [bug]

  Fixed issue where passing a callbale function returning an iterable of column elements to relationship.order_by was flagged as an error in type checkers.

  References: #8776

postgresql

• [postgresql] [usecase]

  Complementing #8690, new comparison methods such as Range.adjacent_to(), Range.difference(), Range.union(), etc., were added to the PG-specific range objects, bringing them in par with the standard operators implemented by the underlying AbstractRange.comparator_factory.

  In addition, the __bool__() method of the class has been corrected to be consistent with the common Python containers behavior as well as how other popular PostgreSQL drivers do: it now tells whether the range instance is not empty, rather than the other way around.

  Pull request courtesy Lele Gaifax.

  References: #8765

• [postgresql] [change] [asyncpg]

  Changed the paramstyle used by asyncpg from format to numeric_dollar. This has two main benefits since it does not require additional processing of the statement and allows for duplicate parameters to be present in the statements.

  References: #8926

• [postgresql] [bug] [mssql]

  For the PostgreSQL and SQL Server dialects only, adjusted the compiler so that when rendering column expressions in the RETURNING clause, the “non anon” label that’s used in SELECT statements is suggested for SQL expression elements that generate a label; the primary example is a SQL function that may be emitting as part of the column’s type, where the label name should match the column’s name by default. This restores a not-well defined behavior that had changed in version 1.4.21 due to #6718, #6710. The Oracle dialect has a different RETURNING implementation and was not affected by this issue. Version 2.0 features an across the board change for its widely expanded support of RETURNING on other backends.

  This change is also backported to: 1.4.44

  References: #8770

• [postgresql] [bug]

  Added additional type-detection for the new PostgreSQL Range type, where previous cases that allowed the psycopg2-native range objects to be received directly by the DBAPI without SQLAlchemy intercepting them stopped working, as we now have our own value object. The Range object has been enhanced such that SQLAlchemy Core detects it in otherwise ambiguous situations (such as comparison to dates) and applies appropriate bind handlers. Pull request courtesy Lele Gaifax.

  References: #8884

mssql

• [mssql] [bug]

  Fixed regression caused by the combination of #8177, re-enable setinputsizes for SQL server unless fast_executemany + DBAPI executemany is used for a statement, along with #6047, implement “insertmanyvalues”, which bypasses DBAPI executemany in place of a custom DBAPI execute for INSERT statements. setinputsizes would incorrectly not be used for a multiple parameter-set INSERT statement that used “insertmanyvalues” if fast_executemany were turned on, as the check would incorrectly assume this is a DBAPI executemany call. The “regression” would then be that the “insertmanyvalues” statement format is apparently slightly more sensitive to multiple rows that don’t use the same types for each row, so in such a case setinputsizes is especially needed.

  The fix repairs the fast_executemany check so that it only disables setinputsizes if true DBAPI executemany is to be used.

  References: #8917

oracle

• [oracle] [bug]

  Continued fixes for Oracle fix #8708 released in 1.4.43 where bound parameter names that start with underscores, which are disallowed by Oracle, were still not being properly escaped in all circumstances.

  This change is also backported to: 1.4.45

  References: #8708

tests

• [tests] [bug]

  Fixed issue where the --disable-asyncio parameter to the test suite would fail to not actually run greenlet tests and would also not prevent the suite from using a “wrapping” greenlet for the whole suite. This parameter now ensures that no greenlet or asyncio use will occur within the entire run when set.

  This change is also backported to: 1.4.44

  References: #8793

2.0.0b3

Released: November 4, 2022

orm

• [orm] [bug]

  Fixed issue in joined eager loading where an assertion fail would occur with a particular combination of outer/inner joined eager loads, when eager loading across three mappers where the middle mapper was an inherited subclass mapper.

  This change is also backported to: 1.4.43

  References: #8738

• [orm] [bug]

  Fixed bug involving Select constructs, where combinations of Select.select_from() with Select.join(), as well as when using Select.join_from(), would cause the with_loader_criteria() feature as well as the IN criteria needed for single-table inheritance queries to not render, in cases where the columns clause of the query did not explicitly include the left-hand side entity of the JOIN. The correct entity is now transferred to the Join object that’s generated internally, so that the criteria against the left side entity is correctly added.

  This change is also backported to: 1.4.43

  References: #8721

• [orm] [bug]

  An informative exception is now raised when the with_loader_criteria() option is used as a loader option added to a specific “loader path”, such as when using it within Load.options(). This use is not supported as with_loader_criteria() is only intended to be used as a top level loader option. Previously, an internal error would be generated.

  This change is also backported to: 1.4.43

  References: #8711

• [orm] [bug]

  Improved “dictionary mode” for Session.get() so that synonym names which refer to primary key attribute names may be indicated in the named dictionary.

  This change is also backported to: 1.4.43

  References: #8753

• [orm] [bug]

  Fixed issue where “selectin_polymorphic” loading for inheritance mappers would not function correctly if the Mapper.polymorphic_on parameter referred to a SQL expression that was not directly mapped on the class.

  This change is also backported to: 1.4.43

  References: #8704

• [orm] [bug]

  Fixed issue where the underlying DBAPI cursor would not be closed when using the Query object as an iterator, if a user-defined exception case were raised within the iteration process, thereby causing the iterator to be closed by the Python interpreter. When using Query.yield_per() to create server-side cursors, this would lead to the usual MySQL-related issues with server side cursors out of sync, and without direct access to the Result object, end-user code could not access the cursor in order to close it.

  To resolve, a catch for GeneratorExit is applied within the iterator method, which will close the result object in those cases when the iterator were interrupted, and by definition will be closed by the Python interpreter.

  As part of this change as implemented for the 1.4 series, ensured that .close() methods are available on all Result implementations including ScalarResult, MappingResult. The 2.0 version of this change also includes new context manager patterns for use with Result classes.

  This change is also backported to: 1.4.43

  References: #8710

orm declarative

• [orm] [declarative] [bug]

  Added support in ORM declarative annotations for class names specified for relationship(), as well as the name of the Mapped symbol itself, to be different names than their direct class name, to support scenarios such as where Mapped is imported as from sqlalchemy.orm import Mapped as M, or where related class names are imported with an alternate name in a similar fashion. Additionally, a target class name given as the lead argument for relationship() will always supersede the name given in the left hand annotation, so that otherwise un-importable names that also don’t match the class name can still be used in annotations.

  References: #8759

• [orm] [declarative] [bug]

  Improved support for legacy 1.4 mappings that use annotations which don’t include Mapped[], by ensuring the __allow_unmapped__ attribute can be used to allow such legacy annotations to pass through Annotated Declarative without raising an error and without being interpreted in an ORM runtime context. Additionally improved the error message generated when this condition is detected, and added more documentation for how this situation should be handled. Unfortunately the 1.4 WARN_SQLALCHEMY_20 migration warning cannot detect this particular configurational issue at runtime with its current architecture.

  References: #8692

• [orm] [declarative] [bug]

  Changed a fundamental configuration behavior of Mapper, where Column objects that are explicitly present in the Mapper.properties dictionary, either directly or enclosed within a mapper property object, will now be mapped within the order of how they appear within the mapped Table (or other selectable) itself (assuming they are in fact part of that table’s list of columns), thereby maintaining the same order of columns in the mapped selectable as is instrumented on the mapped class, as well as what renders in an ORM SELECT statement for that mapper. Previously (where “previously” means since version 0.0.1), Column objects in the Mapper.properties dictionary would always be mapped first, ahead of when the other columns in the mapped Table would be mapped, causing a discrepancy in the order in which the mapper would assign attributes to the mapped class as well as the order in which they would render in statements.

  The change most prominently takes place in the way that Declarative assigns declared columns to the Mapper, specifically how Column (or mapped_column()) objects are handled when they have a DDL name that is explicitly different from the mapped attribute name, as well as when constructs such as deferred() etc. are used. The new behavior will see the column ordering within the mapped Table being the same order in which the attributes are mapped onto the class, assigned within the Mapper itself, and rendered in ORM statements such as SELECT statements, independent of how the Column was configured against the Mapper.

  References: #8705

• [orm] [declarative] [bug]

  Fixed issue in new dataclass mapping feature where a column declared on the decalrative base / abstract base / mixin would leak into the constructor for an inheriting subclass under some circumstances.

  References: #8718

• [bug] [orm declarative]

  Fixed issues within the declarative typing resolver (i.e. which resolves ForwardRef objects) where types that were declared for columns in one particular source file would raise NameError when the ultimate mapped class were in another source file. The types are now resolved in terms of the module for each class in which the types are used.

  References: #8742

engine

• [engine] [feature]

  To better support the use case of iterating Result and AsyncResult objects where user-defined exceptions may interrupt the iteration, both objects as well as variants such as ScalarResult, MappingResult, AsyncScalarResult, AsyncMappingResult now support context manager usage, where the result will be closed at the end of the context manager block.

  In addition, ensured that all the above mentioned Result objects include a Result.close() method as well as Result.closed accessors, including ScalarResult and MappingResult which previously did not have a .close() method.

  See also

  Context Manager Support for Result, AsyncResult

  References: #8710

• [engine] [usecase]

  Added new parameter PoolEvents.reset.reset_state parameter to the PoolEvents.reset() event, with deprecation logic in place that will continue to accept event hooks using the previous set of arguments. This indicates various state information about how the reset is taking place and is used to allow custom reset schemes to take place with full context given.

  Within this change a fix that’s also backported to 1.4 is included which re-enables the PoolEvents.reset() event to continue to take place under all circumstances, including when Connection has already “reset” the connection.

  The two changes together allow custom reset schemes to be implemented using the PoolEvents.reset() event, instead of the PoolEvents.checkin() event (which continues to function as it always has).

  References: #8717

• [engine] [bug] [regression]

  Fixed issue where the PoolEvents.reset() event hook would not be be called in all cases when a Connection were closed and was in the process of returning its DBAPI connection to the connection pool.

  The scenario was when the Connection had already emitted .rollback() on its DBAPI connection within the process of returning the connection to the pool, where it would then instruct the connection pool to forego doing its own “reset” to save on the additional method call. However, this prevented custom pool reset schemes from being used within this hook, as such hooks by definition are doing more than just calling .rollback(), and need to be invoked under all circumstances. This was a regression that appeared in version 1.4.

  For version 1.4, the PoolEvents.checkin() remains viable as an alternate event hook to use for custom “reset” implementations. Version 2.0 will feature an improved version of PoolEvents.reset() which is called for additional scenarios such as termination of asyncio connections, and is also passed contextual information about the reset, to allow for “custom connection reset” schemes which can respond to different reset scenarios in different ways.

  This change is also backported to: 1.4.43

  References: #8717

sql

• [sql] [bug]

  Fixed issue which prevented the literal_column() construct from working properly within the context of a Select construct as well as other potential places where “anonymized labels” might be generated, if the literal expression contained characters which could interfere with format strings, such as open parenthesis, due to an implementation detail of the “anonymous label” structure.

  This change is also backported to: 1.4.43

  References: #8724

typing

• [typing] [bug]

  Corrected various typing issues within the engine and async engine packages.

postgresql

• [postgresql] [feature]

  Added new methods Range.contains() and Range.contained_by() to the new Range data object, which mirror the behavior of the PostgreSQL @> and <@ operators, as well as the comparator_factory.contains() and comparator_factory.contained_by() SQL operator methods. Pull request courtesy Lele Gaifax.

  References: #8706

• [postgresql] [usecase]

  Refined the new approach to range objects described at New RANGE / MULTIRANGE support and changes for PostgreSQL backends to accommodate driver-specific range and multirange objects, to better accommodate both legacy code as well as when passing results from raw SQL result sets back into new range or multirange expressions.

  References: #8690

mssql

• [mssql] [bug]

  Fixed issue with Inspector.has_table(), which when used against a temporary table with the SQL Server dialect would fail on some Azure variants, due to an unnecessary information schema query that is not supported on those server versions. Pull request courtesy Mike Barry.

  This change is also backported to: 1.4.43

  References: #8714

• [mssql] [bug] [reflection]

  Fixed issue with Inspector.has_table(), which when used against a view with the SQL Server dialect would erroneously return False, due to a regression in the 1.4 series which removed support for this on SQL Server. The issue is not present in the 2.0 series which uses a different reflection architecture. Test support is added to ensure has_table() remains working per spec re: views.

  This change is also backported to: 1.4.43

  References: #8700

oracle

• [oracle] [bug]

  Fixed issue where bound parameter names, including those automatically derived from similarly-named database columns, which contained characters that normally require quoting with Oracle would not be escaped when using “expanding parameters” with the Oracle dialect, causing execution errors. The usual “quoting” for bound parameters used by the Oracle dialect is not used with the “expanding parameters” architecture, so escaping for a large range of characters is used instead, now using a list of characters/escapes that are specific to Oracle.

  This change is also backported to: 1.4.43

  References: #8708

• [oracle] [bug]

  Fixed issue where the nls_session_parameters view queried on first connect in order to get the default decimal point character may not be available depending on Oracle connection modes, and would therefore raise an error. The approach to detecting decimal char has been simplified to test a decimal value directly, instead of reading system views, which works on any backend / driver.

  This change is also backported to: 1.4.43

  References: #8744

2.0.0b2

Released: October 20, 2022

orm

• [orm] [bug]

  Removed the warning that emits when using ORM-enabled update/delete regarding evaluation of columns by name, first added in #4073; this warning actually covers up a scenario that otherwise could populate the wrong Python value for an ORM mapped attribute depending on what the actual column is, so this deprecated case is removed. In 2.0, ORM enabled update/delete uses “auto” for “synchronize_session”, which should do the right thing automatically for any given UPDATE expression.

  References: #8656

orm declarative

• [orm] [declarative] [usecase]

  Added support for mapped classes that are also Generic subclasses, to be specified as a GenericAlias object (e.g. MyClass[str]) within statements and calls to inspect().

  References: #8665

• [orm] [declarative] [bug]

  Improved the DeclarativeBase class so that when combined with other mixins like MappedAsDataclass, the order of the classes may be in either order.

  References: #8665

• [orm] [declarative] [bug]

  Fixed bug in new ORM typed declarative mappings where the ability to use Optional[MyClass] or similar forms such as MyClass | None in the type annotation for a many-to-one relationship was not implemented, leading to errors. Documentation has also been added for this use case to the relationship configuration documentation.

  References: #8668

• [orm] [declarative] [bug]

  Fixed issue with new dataclass mapping feature where arguments passed to the dataclasses API could sometimes be mis-ordered when dealing with mixins that override mapped_column() declarations, leading to initializer problems.

  References: #8688

sql

• [sql] [bug] [regression]

  Fixed bug in new “insertmanyvalues” feature where INSERT that included a subquery with bindparam() inside of it would fail to render correctly in “insertmanyvalues” format. This affected psycopg2 most directly as “insertmanyvalues” is used unconditionally with this driver.

  References: #8639

typing

• [typing] [bug]

  Fixed typing issue where pylance strict mode would report “instance variable overrides class variable” when using a method to define __tablename__, __mapper_args__ or __table_args__.

  References: #8645

• [typing] [bug]

  Fixed typing issue where pylance strict mode would report “partially unknown” datatype for the mapped_column() construct.

  References: #8644

mssql

• [mssql] [bug]

  Fixed regression caused by SQL Server pyodbc change #8177 where we now use setinputsizes() by default; for VARCHAR, this fails if the character size is greater than 4000 (or 2000, depending on data) characters as the incoming datatype is NVARCHAR, which has a limit of 4000 characters, despite the fact that VARCHAR can handle unlimited characters. Additional pyodbc-specific typing information is now passed to setinputsizes() when the datatype’s size is > 2000 characters. The change is also applied to the JSON type which was also impacted by this issue for large JSON serializations.

  References: #8661

• [mssql] [bug]

  The Sequence construct restores itself to the DDL behavior it had prior to the 1.4 series, where creating a Sequence with no additional arguments will emit a simple CREATE SEQUENCE instruction without any additional parameters for “start value”. For most backends, this is how things worked previously in any case; however, for MS SQL Server, the default value on this database is -2**63; to prevent this generally impractical default from taking effect on SQL Server, the Sequence.start parameter should be provided. As usage of Sequence is unusual for SQL Server which for many years has standardized on IDENTITY, it is hoped that this change has minimal impact.

  See also

  The Sequence construct reverts to not having any explicit default “start” value; impacts MS SQL Server

  References: #7211

2.0.0b1

Released: October 13, 2022

general

• [general] [changed]

  Migrated the codebase to remove all pre-2.0 behaviors and architectures that were previously noted as deprecated for removal in 2.0, including, but not limited to:

  • removal of all Python 2 code, minimum version is now Python 3.7

  • Engine and Connection now use the new 2.0 style of working, which includes “autobegin”, library level autocommit removed, subtransactions and “branched” connections removed

  • Result objects use 2.0-style behaviors; Row is fully a named tuple without “mapping” behavior, use RowMapping for “mapping” behavior

  • All Unicode encoding/decoding architecture has been removed from SQLAlchemy. All modern DBAPI implementations support Unicode transparently thanks to Python 3, so the convert_unicode feature as well as related mechanisms to look for bytestrings in DBAPI cursor.description etc. have been removed.

  • The .bind attribute and parameter from MetaData, Table, and from all DDL/DML/DQL elements that previously could refer to a “bound engine”

  • The standalone sqlalchemy.orm.mapper() function is removed; all classical mapping should be done through the registry.map_imperatively() method of registry.

  • The Query.join() method no longer accepts strings for relationship names; the long-documented approach of using Class.attrname for join targets is now standard.

  • Query.join() no longer accepts the “aliased” and “from_joinpoint” arguments

  • Query.join() no longer accepts chains of multiple join targets in one method call.

  • Query.from_self(), Query.select_entity_from() and Query.with_polymorphic() are removed.

  • The relationship.cascade_backrefs parameter must now remain at its new default of False; the save-update cascade no longer cascades along a backref.

  • the Session.future parameter must always be set to True. 2.0-style transactional patterns for Session are now always in effect.

  • Loader options no longer accept strings for attribute names. The long-documented approach of using Class.attrname for loader option targets is now standard.

  • Legacy forms of select() removed, including select([cols]), the “whereclause” and keyword parameters of some_table.select().

  • Legacy “in-place mutator” methods on Select such as append_whereclause(), append_order_by() etc are removed.

  • Removed the very old “dbapi_proxy” module, which in very early SQLAlchemy releases was used to provide a transparent connection pool over a raw DBAPI connection.

  References: #7257

• [general] [changed]

  The Query.instances() method is deprecated. The behavioral contract of this method, which is that it can iterate objects through arbitrary result sets, is long obsolete and no longer tested. Arbitrary statements can return objects by using constructs such as :meth`.Select.from_statement` or aliased().

platform

• [platform] [feature]

  The SQLAlchemy C extensions have been replaced with all new implementations written in Cython. Like the C extensions before, pre-built wheel files for a wide range of platforms are available on pypi so that building is not an issue for common platforms. For custom builds, python setup.py build_ext works as before, needing only the additional Cython install. pyproject.toml is also part of the source now which will establish the proper build dependencies when using pip.

  See also

  C Extensions now ported to Cython

  References: #7256

• [platform] [change]

  SQLAlchemy’s source build and installation now includes a pyproject.toml file for full PEP 517 support.

  See also

  Installation is now fully pep-517 enabled

  References: #7311

orm

• [orm] [feature] [sql]

  Added new feature to all included dialects that support RETURNING called “insertmanyvalues”. This is a generalization of the “fast executemany” feature first introduced for the psycopg2 driver in 1.4 at ORM Batch inserts with psycopg2 now batch statements with RETURNING in most cases, which allows the ORM to batch INSERT statements into a much more efficient SQL structure while still being able to fetch newly generated primary key and SQL default values using RETURNING.

  The feature now applies to the many dialects that support RETURNING along with multiple VALUES constructs for INSERT, including all PostgreSQL drivers, SQLite, MariaDB, MS SQL Server. Separately, the Oracle dialect also gains the same capability using native cx_Oracle or OracleDB features.

  References: #6047

• [orm] [feature]

  Added new parameter AttributeEvents.include_key, which will include the dictionary or list key for operations such as __setitem__() (e.g. obj[key] = value) and __delitem__() (e.g. del obj[key]), using a new keyword parameter “key” or “keys”, depending on event, e.g. AttributeEvents.append.key, AttributeEvents.bulk_replace.keys. This allows event handlers to take into account the key that was passed to the operation and is of particular importance for dictionary operations working with MappedCollection.

  References: #8375

• [orm] [feature]

  Added new parameter Operators.op.python_impl, available from Operators.op() and also when using the custom_op constructor directly, which allows an in-Python evaluation function to be provided along with the custom SQL operator. This evaluation function becomes the implementation used when the operator object is used given plain Python objects as operands on both sides, and in particular is compatible with the synchronize_session='evaluate' option used with ORM-Enabled INSERT, UPDATE, and DELETE statements.

  References: #3162

• [orm] [feature]

  The Session (and by extension AsyncSession) now has new state-tracking functionality that will proactively trap any unexpected state changes which occur as a particular transactional method proceeds. This is to allow situations where the Session is being used in a thread-unsafe manner, where event hooks or similar may be calling unexpected methods within operations, as well as potentially under other concurrency situations such as asyncio or gevent to raise an informative message when the illegal access first occurs, rather than passing silently leading to secondary failures due to the Session being in an invalid state.

  See also

  Session raises proactively when illegal concurrent or reentrant access is detected

  References: #7433

• [orm] [feature]

  The composite() mapping construct now supports automatic resolution of values when used with a Python dataclass; the __composite_values__() method no longer needs to be implemented as this method is derived from inspection of the dataclass.

  Additionally, classes mapped by composite now support ordering comparison operations, e.g. <, >=, etc.

  See the new documentation at Composite Column Types for examples.

• [orm] [feature]

  Added very experimental feature to the selectinload() and immediateload() loader options called selectinload.recursion_depth / immediateload.recursion_depth , which allows a single loader option to automatically recurse into self-referential relationships. Is set to an integer indicating depth, and may also be set to -1 to indicate to continue loading until no more levels deep are found. Major internal changes to selectinload() and immediateload() allow this feature to work while continuing to make correct use of the compilation cache, as well as not using arbitrary recursion, so any level of depth is supported (though would emit that many queries). This may be useful for self-referential structures that must be loaded fully eagerly, such as when using asyncio.

  A warning is also emitted when loader options are connected together with arbitrary lengths (that is, without using the new recursion_depth option) when excessive recursion depth is detected in related object loading. This operation continues to use huge amounts of memory and performs extremely poorly; the cache is disabled when this condition is detected to protect the cache from being flooded with arbitrary statements.

  References: #8126

• [orm] [feature]

  Added new parameter Session.autobegin, which when set to False will prevent the Session from beginning a transaction implicitly. The Session.begin() method must be called explicitly first in order to proceed with operations, otherwise an error is raised whenever any operation would otherwise have begun automatically. This option can be used to create a “safe” Session that won’t implicitly start new transactions.

  As part of this change, also added a new status variable origin which may be useful for event handling code to be aware of the origin of a particular SessionTransaction.

  References: #6928

• [orm] [feature]

  Declarative mixins which use Column objects that contain ForeignKey references no longer need to use declared_attr() to achieve this mapping; the ForeignKey object is copied along with the Column itself when the column is applied to the declared mapping.

• [orm] [usecase]

  Added load_only.raiseload parameter to the load_only() loader option, so that the unloaded attributes may have “raise” behavior rather than lazy loading. Previously there wasn’t really a way to do this with the load_only() option directly.

• [orm] [change]

  To better accommodate explicit typing, the names of some ORM constructs that are typically constructed internally, but nonetheless are sometimes visible in messaging as well as typing, have been changed to more succinct names which also match the name of their constructing function (with different casing), in all cases maintaining aliases to the old names for the forseeable future:

  • RelationshipProperty becomes an alias for the primary name Relationship, which is constructed as always from the relationship() function

  • SynonymProperty becomes an alias for the primary name Synonym, constructed as always from the synonym() function

  • CompositeProperty becomes an alias for the primary name Composite, constructed as always from the composite() function

• [orm] [change]

  For consistency with the prominent ORM concept Mapped, the names of the dictionary-oriented collections, attribute_mapped_collection(), column_mapped_collection(), and MappedCollection, are changed to attribute_keyed_dict(), column_keyed_dict() and KeyFuncDict, using the phrase “dict” to minimize any confusion against the term “mapped”. The old names will remain indefinitely with no schedule for removal.

  References: #8608

• [orm] [bug]

  All Result objects will now consistently raise ResourceClosedError if they are used after a hard close, which includes the “hard close” that occurs after calling “single row or value” methods like Result.first() and Result.scalar(). This was already the behavior of the most common class of result objects returned for Core statement executions, i.e. those based on CursorResult, so this behavior is not new. However, the change has been extended to properly accommodate for the ORM “filtering” result objects returned when using 2.0 style ORM queries, which would previously behave in “soft closed” style of returning empty results, or wouldn’t actually “soft close” at all and would continue yielding from the underlying cursor.

  As part of this change, also added Result.close() to the base Result class and implemented it for the filtered result implementations that are used by the ORM, so that it is possible to call the CursorResult.close() method on the underlying CursorResult when the the yield_per execution option is in use to close a server side cursor before remaining ORM results have been fetched. This was again already available for Core result sets but the change makes it available for 2.0 style ORM results as well.

  This change is also backported to: 1.4.27

  References: #7274

• [orm] [bug]

  Fixed issue where the registry.map_declaratively() method would return an internal “mapper config” object and not the Mapper object as stated in the API documentation.

• [orm] [bug]

  Fixed performance regression which appeared at least in version 1.3 if not earlier (sometime after 1.0) where the loading of deferred columns, those explicitly mapped with defer() as opposed to non-deferred columns that were expired, from a joined inheritance subclass would not use the “optimized” query which only queried the immediate table that contains the unloaded columns, instead running a full ORM query which would emit a JOIN for all base tables, which is not necessary when only loading columns from the subclass.

  References: #7463

• [orm] [bug]

  The internals for the Load object and related loader strategy patterns have been mostly rewritten, to take advantage of the fact that only attribute-bound paths, not strings, are now supported. The rewrite hopes to make it more straightforward to address new use cases and subtle issues within the loader strategy system going forward.

  References: #6986

• [orm] [bug]

  Made an improvement to the “deferred” / “load_only” set of strategy options where if a certain object is loaded from two different logical paths within one query, attributes that have been configured by at least one of the options to be populated will be populated in all cases, even if other load paths for that same object did not set this option. previously, it was based on randomness as to which “path” addressed the object first.

  References: #8166

• [orm] [bug]

  Fixed issue in ORM enabled UPDATE when the statement is created against a joined-inheritance subclass, updating only local table columns, where the “fetch” synchronization strategy would not render the correct RETURNING clause for databases that use RETURNING for fetch synchronization. Also adjusts the strategy used for RETURNING in UPDATE FROM and DELETE FROM statements.

  References: #8344

• [orm] [bug] [asyncio]

  Removed the unused **kw arguments from begin and begin_nested. These kw aren’t used and appear to have been added to the API in error.

  References: #7703

• [orm] [bug]

  Changed the attribute access method used by attribute_mapped_collection() and column_mapped_collection() (now called attribute_keyed_dict() and column_keyed_dict()) , used when populating the dictionary, to assert that the data value on the object to be used as the dictionary key is actually present, and is not instead using “None” due to the attribute never being actually assigned. This is used to prevent a mis-population of None for a key when assigning via a backref where the “key” attribute on the object is not yet assigned.

  As the failure mode here is a transitory condition that is not typically persisted to the database, and is easy to produce via the constructor of the class based on the order in which parameters are assigned, it is very possible that many applications include this behavior already which is silently passed over. To accommodate for applications where this error is now raised, a new parameter attribute_keyed_dict.ignore_unpopulated_attribute is also added to both attribute_keyed_dict() and column_keyed_dict() that instead causes the erroneous backref assignment to be skipped.

  References: #8372

• [orm] [bug]

  Added new parameter AbstractConcreteBase.strict_attrs to the AbstractConcreteBase declarative mixin class. The effect of this parameter is that the scope of attributes on subclasses is correctly limited to the subclass in which each attribute is declared, rather than the previous behavior where all attributes of the entire hierarchy are applied to the base “abstract” class. This produces a cleaner, more correct mapping where subclasses no longer have non-useful attributes on them which are only relevant to sibling classes. The default for this parameter is False, which leaves the previous behavior unchanged; this is to support existing code that makes explicit use of these attributes in queries. To migrate to the newer approach, apply explicit attributes to the abstract base class as needed.

  References: #8403

• [orm] [bug]

  The behavior of defer() regarding primary key and “polymorphic discriminator” columns is revised such that these columns are no longer deferrable, either explicitly or when using a wildcard such as defer('*'). Previously, a wildcard deferral would not load PK/polymorphic columns which led to errors in all cases, as the ORM relies upon these columns to produce object identities. The behavior of explicit deferral of primary key columns is unchanged as these deferrals already were implicitly ignored.

  References: #7495

• [orm] [bug]

  Fixed bug in the behavior of the Mapper.eager_defaults parameter such that client-side SQL default or onupdate expressions in the table definition alone will trigger a fetch operation using RETURNING or SELECT when the ORM emits an INSERT or UPDATE for the row. Previously, only server side defaults established as part of table DDL and/or server-side onupdate expressions would trigger this fetch, even though client-side SQL expressions would be included when the fetch was rendered.

  References: #7438

engine

• [engine] [feature]

  The DialectEvents.handle_error() event is now moved to the DialectEvents suite from the EngineEvents suite, and now participates in the connection pool “pre ping” event for those dialects that make use of disconnect codes in order to detect if the database is live. This allows end-user code to alter the state of “pre ping”. Note that this does not include dialects which contain a native “ping” method such as that of psycopg2 or most MySQL dialects.

  References: #5648

• [engine] [feature]

  The ConnectionEvents.set_connection_execution_options() and ConnectionEvents.set_engine_execution_options() event hooks now allow the given options dictionary to be modified in-place, where the new contents will be received as the ultimate execution options to be acted upon. Previously, in-place modifications to the dictionary were not supported.

• [engine] [usecase]

  Generalized the create_engine.isolation_level parameter to the base dialect so that it is no longer dependent on individual dialects to be present. This parameter sets up the “isolation level” setting to occur for all new database connections as soon as they are created by the connection pool, where the value then stays set without being reset on every checkin.

  The create_engine.isolation_level parameter is essentially equivalent in functionality to using the Engine.execution_options.isolation_level parameter via Engine.execution_options() for an engine-wide setting. The difference is in that the former setting assigns the isolation level just once when a connection is created, the latter sets and resets the given level on each connection checkout.

  References: #6342

• [engine] [change]

  Some small API changes regarding engines and dialects:

  • The Dialect.set_isolation_level(), Dialect.get_isolation_level(), :meth: dialect methods will always be passed the raw DBAPI connection

  • The Connection and Engine classes no longer share a base Connectable superclass, which has been removed.

  • Added a new interface class PoolProxiedConnection - this is the public facing interface for the familiar _ConnectionFairy class which is nonetheless a private class.

  References: #7122

• [engine] [bug] [regression]

  Fixed regression where the CursorResult.fetchmany() method would fail to autoclose a server-side cursor (i.e. when stream_results or yield_per is in use, either Core or ORM oriented results) when the results were fully exhausted.

  This change is also backported to: 1.4.27

  References: #7274

• [engine] [bug]

  Fixed issue in future Engine where calling upon Engine.begin() and entering the context manager would not close the connection if the actual BEGIN operation failed for some reason, such as an event handler raising an exception; this use case failed to be tested for the future version of the engine. Note that the “future” context managers which handle begin() blocks in Core and ORM don’t actually run the “BEGIN” operation until the context managers are actually entered. This is different from the legacy version which runs the “BEGIN” operation up front.

  This change is also backported to: 1.4.27

  References: #7272

• [engine] [bug]

  The QueuePool now ignores max_overflow when pool_size=0, properly making the pool unlimited in all cases.

  References: #8523

• [engine] [bug]

  For improved security, the URL object will now use password obfuscation by default when str(url) is called. To stringify a URL with cleartext password, the URL.render_as_string() may be used, passing the URL.render_as_string.hide_password parameter as False. Thanks to our contributors for this pull request.

  See also

  str(engine.url) will obfuscate the password by default

  References: #8567

• [engine] [bug]

  The Inspector.has_table() method will now consistently check for views of the given name as well as tables. Previously this behavior was dialect dependent, with PostgreSQL, MySQL/MariaDB and SQLite supporting it, and Oracle and SQL Server not supporting it. Third party dialects should also seek to ensure their Inspector.has_table() method searches for views as well as tables for the given name.

  References: #7161

• [engine] [bug]

  Fixed issue in Result.columns() method where calling upon Result.columns() with a single index could in some cases, particularly ORM result object cases, cause the Result to yield scalar objects rather than Row objects, as though the Result.scalars() method had been called. In SQLAlchemy 1.4, this scenario emits a warning that the behavior will change in SQLAlchemy 2.0.

  References: #7953

• [engine] [bug]

  Passing a DefaultGenerator object such as a Sequence to the Connection.execute() method is deprecated, as this method is typed as returning a CursorResult object, and not a plain scalar value. The Connection.scalar() method should be used instead, which has been reworked with new internal codepaths to suit invoking a SELECT for default generation objects without going through the Connection.execute() method.

• [engine] [removed]

  Removed the previously deprecated case_sensitive parameter from create_engine(), which would impact only the lookup of string column names in Core-only result set rows; it had no effect on the behavior of the ORM. The effective behavior of what case_sensitive refers towards remains at its default value of True, meaning that string names looked up in row._mapping will match case-sensitively, just like any other Python mapping.

  Note that the case_sensitive parameter was not in any way related to the general subject of case sensitivity control, quoting, and “name normalization” (i.e. converting for databases that consider all uppercase words to be case insensitive) for DDL identifier names, which remains a normal core feature of SQLAlchemy.

• [engine] [removed]

  Removed legacy and deprecated package sqlalchemy.databases. Please use sqlalchemy.dialects instead.

  References: #7258

• [engine] [deprecations]

  The create_engine.implicit_returning parameter is deprecated on the create_engine() function only; the parameter remains available on the Table object. This parameter was originally intended to enable the “implicit returning” feature of SQLAlchemy when it was first developed and was not enabled by default. Under modern use, there’s no reason this parameter should be disabled, and it has been observed to cause confusion as it degrades performance and makes it more difficult for the ORM to retrieve recently inserted server defaults. The parameter remains available on Table to specifically suit database-level edge cases which make RETURNING infeasible, the sole example currently being SQL Server’s limitation that INSERT RETURNING may not be used on a table that has INSERT triggers on it.

  References: #6962

sql

• [sql] [feature]

  Added long-requested case-insensitive string operators ColumnOperators.icontains(), ColumnOperators.istartswith(), ColumnOperators.iendswith(), which produce case-insensitive LIKE compositions (using ILIKE on PostgreSQL, and the LOWER() function on all other backends) to complement the existing LIKE composition operators ColumnOperators.contains(), ColumnOperators.startswith(), etc. Huge thanks to Matias Martinez Rebori for their meticulous and complete efforts in implementing these new methods.

  References: #3482

• [sql] [feature]

  Added new syntax to the FromClause.c collection on all FromClause objects allowing tuples of keys to be passed to __getitem__(), along with support for the select() construct to handle the resulting tuple-like collection directly, allowing the syntax select(table.c['a', 'b', 'c']) to be possible. The sub-collection returned is itself a ColumnCollection which is also directly consumable by select() and similar now.

  See also

  Setting the COLUMNS and FROM clause

  References: #8285

• [sql] [feature]

  Added new backend-agnostic Uuid datatype generalized from the PostgreSQL dialects to now be a core type, as well as migrated UUID from the PostgreSQL dialect. The SQL Server UNIQUEIDENTIFIER datatype also becomes a UUID-handling datatype. Thanks to Trevor Gross for the help on this.

  References: #7212

• [sql] [feature]

  Added Double, DOUBLE, DOUBLE_PRECISION datatypes to the base sqlalchemy. module namespace, for explicit use of double/double precision as well as generic “double” datatypes. Use Double for generic support that will resolve to DOUBLE/DOUBLE PRECISION/FLOAT as needed for different backends.

  References: #5465

• [sql] [usecase]

  Altered the compilation mechanics of the Insert construct such that the “autoincrement primary key” column value will be fetched via cursor.lastrowid or RETURNING even if present in the parameter set or within the Insert.values() method as a plain bound value, for single-row INSERT statements on specific backends that are known to generate autoincrementing values even when explicit NULL is passed. This restores a behavior that was in the 1.3 series for both the use case of separate parameter set as well as Insert.values(). In 1.4, the parameter set behavior unintentionally changed to no longer do this, but the Insert.values() method would still fetch autoincrement values up until 1.4.21 where #6770 changed the behavior yet again again unintentionally as this use case was never covered.

  The behavior is now defined as “working” to suit the case where databases such as SQLite, MySQL and MariaDB will ignore an explicit NULL primary key value and nonetheless invoke an autoincrement generator.

  References: #7998

• [sql] [usecase]

  Added modified ISO-8601 rendering (i.e. ISO-8601 with the T converted to a space) when using literal_binds with the SQL compilers provided by the PostgreSQL, MySQL, MariaDB, MSSQL, Oracle dialects. For Oracle, the ISO format is wrapped inside of an appropriate TO_DATE() function call. Previously this rendering was not implemented for dialect-specific compilation.

  See also

  DATE, TIME, DATETIME datatypes now support literal rendering on all backends

  References: #5052

• [sql] [usecase]

  Added new parameter HasCTE.add_cte.nest_here to HasCTE.add_cte() which will “nest” a given CTE at the level of the parent statement. This parameter is equivalent to using the HasCTE.cte.nesting parameter, but may be more intuitive in some scenarios as it allows the nesting attribute to be set simultaneously along with the explicit level of the CTE.

  The HasCTE.add_cte() method also accepts multiple CTE objects.

  References: #7759

• [sql] [bug]

  The FROM clauses that are established on a select() construct when using the Select.select_from() method will now render first in the FROM clause of the rendered SELECT, which serves to maintain the ordering of clauses as was passed to the Select.select_from() method itself without being affected by the presence of those clauses also being mentioned in other parts of the query. If other elements of the Select also generate FROM clauses, such as the columns clause or WHERE clause, these will render after the clauses delivered by Select.select_from() assuming they were not explictly passed to Select.select_from() also. This improvement is useful in those cases where a particular database generates a desirable query plan based on a particular ordering of FROM clauses and allows full control over the ordering of FROM clauses.

  References: #7888

• [sql] [bug]

  The Enum.length parameter, which sets the length of the VARCHAR column for non-native enumeration types, is now used unconditionally when emitting DDL for the VARCHAR datatype, including when the Enum.native_enum parameter is set to True for target backends that continue to use VARCHAR. Previously the parameter would be erroneously ignored in this case. The warning previously emitted for this case is now removed.

  References: #7791

• [sql] [bug]

  The in-place type detection for Python integers, as occurs with an expression such as literal(25), will now apply value-based adaption as well to accommodate Python large integers, where the datatype determined will be BigInteger rather than Integer. This accommodates for dialects such as that of asyncpg which both sends implicit typing information to the driver as well as is sensitive to numeric scale.

  References: #7909

• [sql] [bug]

  Added if_exists and if_not_exists parameters for all “Create” / “Drop” constructs including CreateSequence, DropSequence, CreateIndex, DropIndex, etc. allowing generic “IF EXISTS” / “IF NOT EXISTS” phrases to be rendered within DDL. Pull request courtesy Jesse Bakker.

  References: #7354

• [sql] [bug]

  Improved the construction of SQL binary expressions to allow for very long expressions against the same associative operator without special steps needed in order to avoid high memory use and excess recursion depth. A particular binary operation A op B can now be joined against another element op C and the resulting structure will be “flattened” so that the representation as well as SQL compilation does not require recursion.

  One effect of this change is that string concatenation expressions which use SQL functions come out as “flat”, e.g. MySQL will now render concat('x', 'y', 'z', ...)` rather than nesting together two-element functions like concat(concat('x', 'y'), 'z'). Third-party dialects which override the string concatenation operator will need to implement a new method def visit_concat_op_expression_clauselist() to accompany the existing def visit_concat_op_binary() method.

  References: #7744

• [sql] [bug]

  Implemented full support for “truediv” and “floordiv” using the “/” and “//” operators. A “truediv” operation between two expressions using Integer now considers the result to be Numeric, and the dialect-level compilation will cast the right operand to a numeric type on a dialect-specific basis to ensure truediv is achieved. For floordiv, conversion is also added for those databases that don’t already do floordiv by default (MySQL, Oracle) and the FLOOR() function is rendered in this case, as well as for cases where the right operand is not an integer (needed for PostgreSQL, others).

  The change resolves issues both with inconsistent behavior of the division operator on different backends and also fixes an issue where integer division on Oracle would fail to be able to fetch a result due to inappropriate outputtypehandlers.

  See also

  Python division operator performs true division for all backends; added floor division

  References: #4926

• [sql] [bug]

  Added an additional lookup step to the compiler which will track all FROM clauses which are tables, that may have the same name shared in multiple schemas where one of the schemas is the implicit “default” schema; in this case, the table name when referring to that name without a schema qualification will be rendered with an anonymous alias name at the compiler level in order to disambiguate the two (or more) names. The approach of schema-qualifying the normally unqualified name with the server-detected “default schema name” value was also considered, however this approach doesn’t apply to Oracle nor is it accepted by SQL Server, nor would it work with multiple entries in the PostgreSQL search path. The name collision issue resolved here has been identified as affecting at least Oracle, PostgreSQL, SQL Server, MySQL and MariaDB.

  References: #7471

• [sql] [bug]

  Python string values for which a SQL type is determined from the type of the value, mainly when using literal(), will now apply the String type, rather than the Unicode datatype, for Python string values that test as “ascii only” using Python str.isascii(). If the string is not isascii(), the Unicode datatype will be bound instead, which was used in all string detection previously. This behavior only applies to in-place detection of datatypes when using ``literal()`` or other contexts that have no existing datatype, which is not usually the case under normal Column comparison operations, where the type of the Column being compared always takes precedence.

  Use of the Unicode datatype can determine literal string formatting on backends such as SQL Server, where a literal value (i.e. using literal_binds) will be rendered as N'<value>' instead of 'value'. For normal bound value handling, the Unicode datatype also may have implications for passing values to the DBAPI, again in the case of SQL Server, the pyodbc driver supports the use of setinputsizes mode which will handle String versus Unicode differently.

  References: #7551

• [sql] [bug]

  The array_agg will now set the array dimensions to 1. Improved ARRAY processing to accept None values as value of a multi-array.

  References: #7083

schema

• [schema] [feature]

  Expanded on the “conditional DDL” system implemented by the ExecutableDDLElement class (renamed from DDLElement) to be directly available on SchemaItem constructs such as Index, ForeignKeyConstraint, etc. such that the conditional logic for generating these elements is included within the default DDL emitting process. This system can also be accommodated by a future release of Alembic to support conditional DDL elements within all schema-management systems.

  See also

  New Conditional DDL for Constraints and Indexes

  References: #7631

• [schema] [usecase]

  Added parameter DropConstraint.if_exists to the DropConstraint construct which result in “IF EXISTS” DDL being added to the DROP statement. This phrase is not accepted by all databases and the operation will fail on a database that does not support it as there is no similarly compatible fallback within the scope of a single DDL statement. Pull request courtesy Mike Fiedler.

  References: #8141

• [schema] [usecase]

  Implemented the DDL event hooks DDLEvents.before_create(), DDLEvents.after_create(), DDLEvents.before_drop(), DDLEvents.after_drop() for all SchemaItem objects that include a distinct CREATE or DROP step, when that step is invoked as a distinct SQL statement, including for ForeignKeyConstraint, Sequence, Index, and PostgreSQL’s ENUM.

  References: #8394

• [schema] [performance]

  Rearchitected the schema reflection API to allow participating dialects to make use of high performing batch queries to reflect the schemas of many tables at once using fewer queries by an order of magnitude. The new performance features are targeted first at the PostgreSQL and Oracle backends, and may be applied to any dialect that makes use of SELECT queries against system catalog tables to reflect tables. The change also includes new API features and behavioral improvements to the Inspector object, including consistent, cached behavior of methods like Inspector.has_table(), Inspector.get_table_names() and new methods Inspector.has_schema() and Inspector.has_index().

  See also

  Major Architectural, Performance and API Enhancements for Database Reflection - full background

  References: #4379

• [schema] [bug]

  The warnings that are emitted regarding reflection of indexes or unique constraints, when the Table.include_columns parameter is used to exclude columns that are then found to be part of those constraints, have been removed. When the Table.include_columns parameter is used it should be expected that the resulting Table construct will not include constraints that rely upon omitted columns. This change was made in response to #8100 which repaired Table.include_columns in conjunction with foreign key constraints that rely upon omitted columns, where the use case became clear that omitting such constraints should be expected.

  References: #8102

• [schema] [postgresql]

  Added support for comments on Constraint objects, including DDL and reflection; the field is added to the base Constraint class and corresponding constructors, however PostgreSQL is the only included backend to support the feature right now. See parameters such as ForeignKeyConstraint.comment, UniqueConstraint.comment or CheckConstraint.comment.

  References: #5677

• [schema] [mariadb] [mysql]

  Add support for Partitioning and Sample pages on MySQL and MariaDB reflected options. The options are stored in the table dialect options dictionary, so the following keyword need to be prefixed with mysql_ or mariadb_ depending on the backend. Supported options are:

  • stats_sample_pages

  • partition_by

  • partitions

  • subpartition_by

  These options are also reflected when loading a table from database, and will populate the table Table.dialect_options. Pull request courtesy of Ramon Will.

  References: #4038

typing

• [typing] [improvement]

  The TypeEngine.with_variant() method now returns a copy of the original TypeEngine object, rather than wrapping it inside the Variant class, which is effectively removed (the import symbol remains for backwards compatibility with code that may be testing for this symbol). While the previous approach maintained in-Python behaviors, maintaining the original type allows for clearer type checking and debugging.

  TypeEngine.with_variant() also accepts multiple dialect names per call as well, in particular this is helpful for related backend names such as "mysql", "mariadb".

  See also

  “with_variant()” clones the original TypeEngine rather than changing the type

  References: #6980

postgresql

• [postgresql] [feature]

  Added a new PostgreSQL DOMAIN datatype, which follows the same CREATE TYPE / DROP TYPE behaviors as that of PostgreSQL ENUM. Much thanks to David Baumgold for the efforts on this.

  See also

  DOMAIN

  References: #7316

• [postgresql] [usecase] [asyncpg]

  Added overridable methods PGDialect_asyncpg.setup_asyncpg_json_codec and PGDialect_asyncpg.setup_asyncpg_jsonb_codec codec, which handle the required task of registering JSON/JSONB codecs for these datatypes when using asyncpg. The change is that methods are broken out as individual, overridable methods to support third party dialects that need to alter or disable how these particular codecs are set up.

  This change is also backported to: 1.4.27

  References: #7284

• [postgresql] [usecase]

  Added literal type rendering for the ARRAY and ARRAY datatypes. The generic stringify will render using brackets, e.g. [1, 2, 3] and the PostgreSQL specific will use the ARRAY literal e.g. ARRAY[1, 2, 3]. Multiple dimensions and quoting are also taken into account.

  References: #8138

• [postgresql] [usecase]

  Adds support for PostgreSQL multirange types, introduced in PostgreSQL 14. Support for PostgreSQL ranges and multiranges has now been generalized to the psycopg3, psycopg2 and asyncpg backends, with room for further dialect support, using a backend-agnostic Range data object that’s constructor-compatible with the previously used psycopg2 object. See the new documentation for usage patterns.

  In addition, range type handling has been enhanced so that it automatically renders type casts, so that in-place round trips for statements that don’t provide the database with any context don’t require the cast() construct to be explicit for the database to know the desired type (discussed at #8540).

  Thanks very much to @zeeeeeb for the pull request implementing and testing the new datatypes and psycopg support.

  See also

  New RANGE / MULTIRANGE support and changes for PostgreSQL backends

  Range and Multirange Types

  References: #7156, #8540

• [postgresql] [usecase]

  The “ping” query emitted when configuring create_engine.pool_pre_ping for psycopg, asyncpg and pg8000, but not for psycopg2, has been changed to be an empty query (;) instead of SELECT 1; additionally, for the asyncpg driver, the unnecessary use of a prepared statement for this query has been fixed. Rationale is to eliminate the need for PostgreSQL to produce a query plan when the ping is emitted. The operation is not currently supported by the psycopg2 driver which continues to use SELECT 1.

  References: #8491

• [postgresql] [change]

  SQLAlchemy now requires PostgreSQL version 9 or greater. Older versions may still work in some limited use cases.

• [postgresql] [change] [mssql]

  The parameter UUID.as_uuid of UUID, previously specific to the PostgreSQL dialect but now generalized for Core (along with a new backend-agnostic Uuid datatype) now defaults to True, indicating that Python UUID objects are accepted by this datatype by default. Additionally, the SQL Server UNIQUEIDENTIFIER datatype has been converted to be a UUID-receiving type; for legacy code that makes use of UNIQUEIDENTIFIER using string values, set the UNIQUEIDENTIFIER.as_uuid parameter to False.

  References: #7225

• [postgresql] [change]

  The ENUM.name parameter for the PostgreSQL-specific ENUM datatype is now a required keyword argument. The “name” is necessary in any case in order for the ENUM to be usable as an error would be raised at SQL/DDL render time if “name” were not present.

• [postgresql] [change]

  In support of new PostgreSQL features including the psycopg3 dialect as well as extended “fast insertmany” support, the system by which typing information for bound parameters is passed to the PostgreSQL database has been redesigned to use inline casts emitted by the SQL compiler, and is now applied to all PostgreSQL dialects. This is in contrast to the previous approach which would rely upon the DBAPI in use to render these casts itself, which in cases such as that of pg8000 and the adapted asyncpg driver, would use the pep-249 setinputsizes() method, or with the psycopg2 driver would rely on the driver itself in most cases, with some special exceptions made for ARRAY.

  The new approach now has all PostgreSQL dialects rendering these casts as needed using PostgreSQL double-colon style within the compiler, and the use of setinputsizes() is removed for PostgreSQL dialects, as this was not generally part of these DBAPIs in any case (pg8000 being the only exception, which added the method at the request of SQLAlchemy developers).

  Advantages to this approach include per-statement performance, as no second pass over the compiled statement is required at execution time, better support for all DBAPIs, as there is now one consistent system of applying typing information, and improved transparency, as the SQL logging output, as well as the string output of a compiled statement, will show these casts present in the statement directly, whereas previously these casts were not visible in logging output as they would occur after the statement were logged.

• [postgresql] [bug]

  The Operators.match() operator now uses plainto_tsquery() for PostgreSQL full text search, rather than to_tsquery(). The rationale for this change is to provide better cross-compatibility with match on other database backends. Full support for all PostgreSQL full text functions remains available through the use of func in conjunction with Operators.bool_op() (an improved version of Operators.op() for boolean operators).

  See also

  match() operator on PostgreSQL uses plainto_tsquery() rather than to_tsquery()

  References: #7086

• [postgresql] [removed]

  Removed support for multiple deprecated drivers:

  • pypostgresql for PostgreSQL. This is available as an external driver at https://github.com/PyGreSQL

  • pygresql for PostgreSQL.

  Please switch to one of the supported drivers or to the external version of the same driver.

  References: #7258

• [postgresql] [dialect]

  Added support for psycopg dialect supporting both sync and async execution. This dialect is available under the postgresql+psycopg name for both the create_engine() and create_async_engine() engine-creation functions.

  See also

  Dialect support for psycopg 3 (a.k.a. “psycopg”)

  psycopg

  References: #6842

• [postgresql] [psycopg2]

  Update psycopg2 dialect to use the DBAPI interface to execute two phase transactions. Previously SQL commands were execute to handle this kind of transactions.

  References: #7238

• [postgresql] [schema]

  Introduced the type JSONPATH that can be used in cast expressions. This is required by some PostgreSQL dialects when using functions such as jsonb_path_exists or jsonb_path_match that accept a jsonpath as input.

  See also

  JSON Types - PostgreSQL JSON types.

  References: #8216

• [postgresql] [reflection]

  The PostgreSQL dialect now supports reflection of expression based indexes. The reflection is supported both when using Inspector.get_indexes() and when reflecting a Table using Table.autoload_with. Thanks to immerrr and Aidan Kane for the help on this ticket.

  References: #7442

mysql

• [mysql] [usecase] [mariadb]

  The ROLLUP function will now correctly render WITH ROLLUP on MySql and MariaDB, allowing the use of group by rollup with these backend.

  References: #8503

• [mysql] [bug]

  Fixed issue in MySQL Insert.on_duplicate_key_update() which would render the wrong column name when an expression were used in a VALUES expression. Pull request courtesy Cristian Sabaila.

  This change is also backported to: 1.4.27

  References: #7281

• [mysql] [removed]

  Removed support for the OurSQL driver for MySQL and MariaDB, as this driver does not seem to be maintained.

  References: #7258

mariadb

• [mariadb] [usecase]

  Added a new execution option is_delete_using=True, which is consumed by the ORM when using an ORM-enabled DELETE statement in conjunction with the “fetch” synchronization strategy; this option indicates that the DELETE statement is expected to use multiple tables, which on MariaDB is the DELETE..USING syntax. The option then indicates that RETURNING (newly implemented in SQLAlchemy 2.0 for MariaDB for #7011) should not be used for databases that are known to not support “DELETE..USING..RETURNING” syntax, even though they support “DELETE..USING”, which is MariaDB’s current capability.

  The rationale for this option is that the current workings of ORM-enabled DELETE doesn’t know up front if a DELETE statement is against multiple tables or not until compilation occurs, which is cached in any case, yet it needs to be known so that a SELECT for the to-be-deleted row can be emitted up front. Instead of applying an across-the-board performance penalty for all DELETE statements by proactively checking them all for this relatively unusual SQL pattern, the is_delete_using=True execution option is requested via a new exception message that is raised within the compilation step. This exception message is specifically (and only) raised when: the statement is an ORM-enabled DELETE where the “fetch” synchronization strategy has been requested; the backend is MariaDB or other backend with this specific limitation; the statement has been detected within the initial compilation that it would otherwise emit “DELETE..USING..RETURNING”. By applying the execution option, the ORM knows to run a SELECT upfront instead. A similar option is implemented for ORM-enabled UPDATE but there is not currently a backend where it is needed.

  References: #8344

• [mariadb] [usecase]

  Added INSERT..RETURNING and DELETE..RETURNING support for the MariaDB dialect. UPDATE..RETURNING is not yet supported by MariaDB. MariaDB supports INSERT..RETURNING as of 10.5.0 and DELETE..RETURNING as of 10.0.5.

  References: #7011

sqlite

• [sqlite] [usecase]

  Added new parameter to SQLite for reflection methods called sqlite_include_internal=True; when omitted, local tables that start with the prefix sqlite_, which per SQLite documentation are noted as “internal schema” tables such as the sqlite_sequence table generated to support “AUTOINCREMENT” columns, will not be included in reflection methods that return lists of local objects. This prevents issues for example when using Alembic autogenerate, which previously would consider these SQLite-generated tables as being remove from the model.

  See also

  Reflecting internal schema tables

  References: #8234

• [sqlite] [usecase]

  Added RETURNING support for the SQLite dialect. SQLite supports RETURNING since version 3.35.

  References: #6195

• [sqlite] [usecase] [performance]

  SQLite datetime, date, and time datatypes now use Python standard lib fromisoformat() methods in order to parse incoming datetime, date, and time string values. This improves performance vs. the previous regular expression-based approach, and also automatically accommodates for datetime and time formats that contain either a six-digit “microseconds” format or a three-digit “milliseconds” format.

  References: #7029

• [sqlite] [usecase]

  The SQLite dialect now supports UPDATE..FROM syntax, for UPDATE statements that may refer to additional tables within the WHERE criteria of the statement without the need to use subqueries. This syntax is invoked automatically when using the Update construct when more than one table or other entity or selectable is used.

  References: #7185

• [sqlite] [bug]

  Removed the warning that emits from the Numeric type about DBAPIs not supporting Decimal values natively. This warning was oriented towards SQLite, which does not have any real way without additional extensions or workarounds of handling precision numeric values more than 15 significant digits as it only uses floating point math to represent numbers. As this is a known and documented limitation in SQLite itself, and not a quirk of the pysqlite driver, there’s no need for SQLAlchemy to warn for this. The change does not otherwise modify how precision numerics are handled. Values can continue to be handled as Decimal() or float() as configured with the Numeric, Float , and related datatypes, just without the ability to maintain precision beyond 15 significant digits when using SQLite, unless alternate representations such as strings are used.

  References: #7299

• [sqlite] [bug] [performance]

  The SQLite dialect now defaults to QueuePool when a file based database is used. This is set along with setting the check_same_thread parameter to False. It has been observed that the previous approach of defaulting to NullPool, which does not hold onto database connections after they are released, did in fact have a measurable negative performance impact. As always, the pool class is customizable via the create_engine.poolclass parameter.

  See also

  The SQLite dialect uses QueuePool for file-based databases

  References: #7490

mssql

• [mssql] [usecase]

  Implemented reflection of the “clustered index” flag mssql_clustered for the SQL Server dialect. Pull request courtesy John Lennox.

  References: #8288

• [mssql] [usecase]

  Added support table and column comments on MSSQL when creating a table. Added support for reflecting table comments. Thanks to Daniel Hall for the help in this pull request.

  References: #7844

• [mssql] [bug]

  The use_setinputsizes parameter for the mssql+pyodbc dialect now defaults to True; this is so that non-unicode string comparisons are bound by pyodbc to pyodbc.SQL_VARCHAR rather than pyodbc.SQL_WVARCHAR, allowing indexes against VARCHAR columns to take effect. In order for the fast_executemany=True parameter to continue functioning, the use_setinputsizes mode now skips the cursor.setinputsizes() call specifically when fast_executemany is True and the specific method in use is cursor.executemany(), which doesn’t support setinputsizes. The change also adds appropriate pyodbc DBAPI typing to values that are typed as Unicode or UnicodeText, as well as altered the base JSON datatype to consider JSON string values as Unicode rather than String.

  References: #8177

• [mssql] [removed]

  Removed support for the mxodbc driver due to lack of testing support. ODBC users may use the pyodbc dialect which is fully supported.

  References: #7258

oracle

• [oracle] [feature]

  Add support for the new oracle driver oracledb.

  See also

  Dialect support for oracledb

  python-oracledb

  References: #8054

• [oracle] [feature]

  Implemented DDL and reflection support for FLOAT datatypes which include an explicit “binary_precision” value. Using the Oracle-specific FLOAT datatype, the new parameter FLOAT.binary_precision may be specified which will render Oracle’s precision for floating point types directly. This value is interpreted during reflection. Upon reflecting back a FLOAT datatype, the datatype returned is one of DOUBLE_PRECISION for a FLOAT for a precision of 126 (this is also Oracle’s default precision for FLOAT), REAL for a precision of 63, and FLOAT for a custom precision, as per Oracle documentation.

  As part of this change, the generic Float.precision value is explicitly rejected when generating DDL for Oracle, as this precision cannot be accurately converted to “binary precision”; instead, an error message encourages the use of TypeEngine.with_variant() so that Oracle’s specific form of precision may be chosen exactly. This is a backwards-incompatible change in behavior, as the previous “precision” value was silently ignored for Oracle.

  See also

  New Oracle FLOAT type with binary precision; decimal precision not accepted directly

  References: #5465

• [oracle] [feature]

  Full “RETURNING” support is implemented for the cx_Oracle dialect, covering two individual types of functionality:

  • multi-row RETURNING is implemented, meaning multiple RETURNING rows are now received for DML statements that produce more than one row for RETURNING.

  • ”executemany RETURNING” is also implemented - this allows RETURNING to yield row-per statement when cursor.executemany() is used. The implementation of this part of the feature delivers dramatic performance improvements to ORM inserts, in the same way as was added for psycopg2 in the SQLAlchemy 1.4 change ORM Batch inserts with psycopg2 now batch statements with RETURNING in most cases.

  References: #6245

• [oracle] [usecase]

  Oracle will now use FETCH FIRST N ROWS / OFFSET syntax for limit/offset support by default for Oracle 12c and above. This syntax was already available when Select.fetch() were used directly, it’s now implied for Select.limit() and Select.offset() as well.

  References: #8221

• [oracle] [change]

  Materialized views on oracle are now reflected as views. On previous versions of SQLAlchemy the views were returned among the table names, not among the view names. As a side effect of this change they are not reflected by default by MetaData.reflect(), unless views=True is set. To get a list of materialized views, use the new inspection method Inspector.get_materialized_view_names().

• [oracle] [bug]

  Adjustments made to the BLOB / CLOB / NCLOB datatypes in the cx_Oracle and oracledb dialects, to improve performance based on recommendations from Oracle developers.

  References: #7494

• [oracle] [bug]

  Related to the deprecation for create_engine.implicit_returning, the “implicit_returning” feature is now enabled for the Oracle dialect in all cases; previously, the feature would be turned off when an Oracle 8/8i version were detected, however online documentation indicates both versions support the same RETURNING syntax as modern versions.

  References: #6962

• [oracle]

  cx_Oracle 7 is now the minimum version for cx_Oracle.

misc

• [removed] [sybase]

  Removed the “sybase” internal dialect that was deprecated in previous SQLAlchemy versions. Third party dialect support is available.

  See also

  External Dialects

  References: #7258

• [removed] [firebird]

  Removed the “firebird” internal dialect that was deprecated in previous SQLAlchemy versions. Third party dialect support is available.

  See also

  External Dialects

  References: #7258