diff options
Diffstat (limited to 'lib/sqlalchemy/dialects/postgresql/base.py')
| -rw-r--r-- | lib/sqlalchemy/dialects/postgresql/base.py | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py index 8eb116111..6550dd20d 100644 --- a/lib/sqlalchemy/dialects/postgresql/base.py +++ b/lib/sqlalchemy/dialects/postgresql/base.py @@ -152,12 +152,44 @@ Valid values for ``isolation_level`` include: .. seealso:: + :ref:`postgresql_readonly_deferrable` + :ref:`dbapi_autocommit` :ref:`psycopg2_isolation_level` :ref:`pg8000_isolation_level` +.. _postgresql_readonly_deferrable: + +Setting READ ONLY / DEFERRABLE +------------------------------ + +Most PostgreSQL dialects support setting the "READ ONLY" and "DEFERRABLE" +characteristics of the transaction, which is in addition to the isolation level +setting. These two attributes can be established either in conjunction with or +independently of the isolation level by passing the ``postgresql_readonly`` and +``postgresql_deferrable`` flags with +:meth:`_engine.Connection.execution_options`. The example below illustrates +passing the ``"SERIALIZABLE"`` isolation level at the same time as setting +"READ ONLY" and "DEFERRABLE":: + + with engine.connect() as conn: + conn = conn.execution_options( + isolation_level="SERIALIZABLE", + postgresql_readonly=True, + postgresql_deferrable=True + ) + with conn.begin(): + # ... work with transaction + +Note that some DBAPIs such as asyncpg only support "readonly" with +SERIALIZABLE isolation. + +.. versionadded:: 1.4 added support for the ``postgresql_readonly`` + and ``postgresql_deferrable`` execution options. + + .. _postgresql_schema_reflection: Remote-Schema Table Introspection and PostgreSQL search_path @@ -1037,6 +1069,7 @@ from ... import exc from ... import schema from ... import sql from ... import util +from ...engine import characteristics from ...engine import default from ...engine import reflection from ...sql import coercions @@ -2610,6 +2643,36 @@ class PGExecutionContext(default.DefaultExecutionContext): return AUTOCOMMIT_REGEXP.match(statement) +class PGReadOnlyConnectionCharacteristic( + characteristics.ConnectionCharacteristic +): + transactional = True + + def reset_characteristic(self, dialect, dbapi_conn): + dialect.set_readonly(dbapi_conn, False) + + def set_characteristic(self, dialect, dbapi_conn, value): + dialect.set_readonly(dbapi_conn, value) + + def get_characteristic(self, dialect, dbapi_conn): + return dialect.get_readonly(dbapi_conn) + + +class PGDeferrableConnectionCharacteristic( + characteristics.ConnectionCharacteristic +): + transactional = True + + def reset_characteristic(self, dialect, dbapi_conn): + dialect.set_deferrable(dbapi_conn, False) + + def set_characteristic(self, dialect, dbapi_conn, value): + dialect.set_deferrable(dbapi_conn, value) + + def get_characteristic(self, dialect, dbapi_conn): + return dialect.get_deferrable(dbapi_conn) + + class PGDialect(default.DefaultDialect): name = "postgresql" supports_alter = True @@ -2645,6 +2708,16 @@ class PGDialect(default.DefaultDialect): implicit_returning = True full_returning = True + connection_characteristics = ( + default.DefaultDialect.connection_characteristics + ) + connection_characteristics = connection_characteristics.union( + { + "postgresql_readonly": PGReadOnlyConnectionCharacteristic(), + "postgresql_deferrable": PGDeferrableConnectionCharacteristic(), + } + ) + construct_arguments = [ ( schema.Index, @@ -2762,6 +2835,18 @@ class PGDialect(default.DefaultDialect): cursor.close() return val.upper() + def set_readonly(self, connection, value): + raise NotImplementedError() + + def get_readonly(self, connection): + raise NotImplementedError() + + def set_deferrable(self, connection, value): + raise NotImplementedError() + + def get_deferrable(self, connection): + raise NotImplementedError() + def do_begin_twophase(self, connection, xid): self.do_begin(connection.connection) |