Commands¶
Note
this section discusses the internal API of Alembic as regards its command invocation system. This section is only useful for developers who wish to extend the capabilities of Alembic. For documentation on using Alembic commands, please see Tutorial.
Alembic commands are all represented by functions in the Commands
package. They all accept the same style of usage, being sent
the Config
object as the first argument.
Commands can be run programmatically, by first constructing a Config
object, as in:
from alembic.config import Config
from alembic import command
alembic_cfg = Config("/path/to/yourapp/alembic.ini")
command.upgrade(alembic_cfg, "head")
In many cases, and perhaps more often than not, an application will wish
to call upon a series of Alembic commands and/or other features. It is
usually a good idea to link multiple commands along a single connection
and transaction, if feasible. This can be achieved using the
Config.attributes
dictionary in order to share a connection:
with engine.begin() as connection:
alembic_cfg.attributes['connection'] = connection
command.upgrade(alembic_cfg, "head")
This recipe requires that env.py
consumes this connection argument;
see the example in Sharing a Connection across one or more programmatic migration commands for details.
To write small API functions that make direct use of database and script directory
information, rather than just running one of the built-in commands,
use the ScriptDirectory
and MigrationContext
classes directly.
- alembic.command.branches(config, verbose=False)¶
Show current branch points.
- Parameters:
config – a
Config
instance.verbose – output in verbose mode.
- alembic.command.check(config: Config) None ¶
Check if revision command with autogenerate has pending upgrade ops.
- Parameters:
config – a
Config
object.
New in version 1.9.0.
- alembic.command.current(config: Config, verbose: bool = False) None ¶
Display the current revision for a database.
- Parameters:
config – a
Config
instance.verbose – output in verbose mode.
- alembic.command.downgrade(config: Config, revision: str, sql: bool = False, tag: str | None = None) None ¶
Revert to a previous version.
- Parameters:
config – a
Config
instance.revision – string revision target or range for –sql mode
sql – if True, use
--sql
modetag – an arbitrary “tag” that can be intercepted by custom
env.py
scripts via theEnvironmentContext.get_tag_argument()
method.
- alembic.command.edit(config: Config, rev: str) None ¶
Edit revision script(s) using $EDITOR.
- Parameters:
config – a
Config
instance.rev – target revision.
- alembic.command.ensure_version(config: Config, sql: bool = False) None ¶
Create the alembic version table if it doesn’t exist already .
- Parameters:
config – a
Config
instance.sql –
use
--sql
modeNew in version 1.7.6.
- alembic.command.heads(config, verbose=False, resolve_dependencies=False)¶
Show current available heads in the script directory.
- Parameters:
config – a
Config
instance.verbose – output in verbose mode.
resolve_dependencies – treat dependency version as down revisions.
- alembic.command.history(config: Config, rev_range: str | None = None, verbose: bool = False, indicate_current: bool = False) None ¶
List changeset scripts in chronological order.
- Parameters:
config – a
Config
instance.rev_range – string revision range
verbose – output in verbose mode.
indicate_current – indicate current revision.
- alembic.command.init(config: Config, directory: str, template: str = 'generic', package: bool = False) None ¶
Initialize a new scripts directory.
- Parameters:
config – a
Config
object.directory – string path of the target directory
template – string name of the migration environment template to use.
package – when True, write
__init__.py
files into the environment location as well as the versions/ location.
- alembic.command.list_templates(config: Config)¶
List available templates.
- Parameters:
config – a
Config
object.
- alembic.command.merge(config: Config, revisions: _RevIdType, message: str | None = None, branch_label: _RevIdType | None = None, rev_id: str | None = None) Script | None ¶
Merge two revisions together. Creates a new migration file.
- Parameters:
config – a
Config
instancemessage – string message to apply to the revision
branch_label – string label name to apply to the new revision
rev_id – hardcoded revision identifier instead of generating a new one.
See also
- alembic.command.revision(config: Config, message: str | None = None, autogenerate: bool = False, sql: bool = False, head: str = 'head', splice: bool = False, branch_label: _RevIdType | None = None, version_path: str | None = None, rev_id: str | None = None, depends_on: str | None = None, process_revision_directives: ProcessRevisionDirectiveFn | None = None) Script | None | List[Script | None] ¶
Create a new revision file.
- Parameters:
config – a
Config
object.message – string message to apply to the revision; this is the
-m
option toalembic revision
.autogenerate – whether or not to autogenerate the script from the database; this is the
--autogenerate
option toalembic revision
.sql – whether to dump the script out as a SQL string; when specified, the script is dumped to stdout. This is the
--sql
option toalembic revision
.head – head revision to build the new revision upon as a parent; this is the
--head
option toalembic revision
.splice – whether or not the new revision should be made into a new head of its own; is required when the given
head
is not itself a head. This is the--splice
option toalembic revision
.branch_label – string label to apply to the branch; this is the
--branch-label
option toalembic revision
.version_path – string symbol identifying a specific version path from the configuration; this is the
--version-path
option toalembic revision
.rev_id – optional revision identifier to use instead of having one generated; this is the
--rev-id
option toalembic revision
.depends_on – optional list of “depends on” identifiers; this is the
--depends-on
option toalembic revision
.process_revision_directives – this is a callable that takes the same form as the callable described at
EnvironmentContext.configure.process_revision_directives
; will be applied to the structure generated by the revision process where it can be altered programmatically. Note that unlike all the other parameters, this option is only available via programmatic use ofcommand.revision()
- alembic.command.show(config, rev)¶
Show the revision(s) denoted by the given symbol.
- Parameters:
config – a
Config
instance.revision – string revision target
- alembic.command.stamp(config: Config, revision: _RevIdType, sql: bool = False, tag: str | None = None, purge: bool = False) None ¶
‘stamp’ the revision table with the given revision; don’t run any migrations.
- Parameters:
config – a
Config
instance.revision –
target revision or list of revisions. May be a list to indicate stamping of multiple branch heads.
Note
this parameter is called “revisions” in the command line interface.
sql – use
--sql
modetag – an arbitrary “tag” that can be intercepted by custom
env.py
scripts via theEnvironmentContext.get_tag_argument
method.purge – delete all entries in the version table before stamping.
- alembic.command.upgrade(config: Config, revision: str, sql: bool = False, tag: str | None = None) None ¶
Upgrade to a later version.
- Parameters:
config – a
Config
instance.revision – string revision target or range for –sql mode
sql – if True, use
--sql
modetag – an arbitrary “tag” that can be intercepted by custom
env.py
scripts via theEnvironmentContext.get_tag_argument()
method.