crdb – CockroachDB support#

New in version 3.1.

CockroachDB is a distributed database using the same fronted-backend protocol of PostgreSQL. As such, Psycopg can be used to write Python programs interacting with CockroachDB.

Opening a connection to a CRDB database using psycopg.connect() provides a largely working object. However, using the psycopg.crdb.connect() function instead, Psycopg will create more specialised objects and provide a types mapping tweaked on the CockroachDB data model.

Main differences from PostgreSQL#

CockroachDB behaviour is different from PostgreSQL: please refer to the database documentation for details. These are some of the main differences affecting Psycopg behaviour:

  • cancel() doesn’t work before CockroachDB 22.1. On older versions, you can use CANCEL QUERY instead (but from a different connection).

  • Server-side cursors are well supported only from CockroachDB 22.1.3.

  • backend_pid is only populated from CockroachDB 22.1. Note however that you cannot use the PID to terminate the session; use SHOW session_id to find the id of a session, which you may terminate with CANCEL SESSION in lieu of PostgreSQL’s pg_terminate_backend().

  • Several data types are missing or slightly different from PostgreSQL (see adapters for an overview of the differences).

  • The two-phase commit protocol is not supported.

  • LISTEN and NOTIFY are not supported. However the CHANGEFEED command, in conjunction with stream(), can provide push notifications.

CockroachDB-specific objects#

psycopg.crdb.connect(conninfo='', **kwargs)#

Connect to a database server and return a new CrdbConnection instance.

Return type:

CrdbConnection[Any]

This is an alias of the class method CrdbConnection.connect.

If you need an asynchronous connection use the AsyncCrdbConnection.connect() method instead.

class psycopg.crdb.CrdbConnection(pgconn, row_factory=<function tuple_row>)#

Wrapper for a connection to a CockroachDB database.

psycopg.Connection subclass.

classmethod is_crdb(conn)#

Return !True if the server connected to !conn is CockroachDB.

Return type:

bool

Parameters:

conn (~psycopg.Connection, ~psycopg.AsyncConnection, ~psycopg.pq.PGconn) – the connection to check

class psycopg.crdb.AsyncCrdbConnection(pgconn, row_factory=<function tuple_row>)#

Wrapper for an async connection to a CockroachDB database.

psycopg.AsyncConnection subclass.

class psycopg.crdb.CrdbConnectionInfo(pgconn)#

~psycopg.ConnectionInfo subclass to get info about a CockroachDB database.

The object is returned by the ~psycopg.Connection.info attribute of CrdbConnection and AsyncCrdbConnection.

The object behaves like !ConnectionInfo, with the following differences:

vendor#

The CockroachDB string.

server_version#

Return the CockroachDB server version connected.

Return a number in the PostgreSQL format (e.g. 21.2.10 -> 210210).

psycopg.crdb.adapters#

The default adapters map establishing how Python and CockroachDB types are converted into each other.

The map is used as a template when new connections are created, using psycopg.crdb.connect() (similarly to the way psycopg.adapters is used as template for new PostgreSQL connections).

This registry contains only the types and adapters supported by CockroachDB. Several PostgreSQL types and adapters are missing or different from PostgreSQL, among which:

  • Composite types

  • range, multirange types

  • The hstore type

  • Geometric types

  • Nested arrays

  • Arrays of jsonb

  • The cidr data type

  • The json type is an alias for jsonb

  • The int type is an alias for int8, not int4.