sqlalchemy.dialects.postgresql.ENUM

PostgreSQL ENUM type. This is a subclass of :class:`_types.Enum` which includes support for PG's ``CREATE TYPE`` and ``DROP TYPE``. When the builtin type :class:`_types.Enum` is used and the :paramref:`.Enum.native_enum` flag is left at its default of True, the PostgreSQL backend will use a :class:`_postgresql.ENUM` type as the implementation, so the special create/drop rules will be used. The create/drop behavior of ENUM is necessarily intricate, due to the awkward relationship the ENUM type has in relationship to the parent table, in that it may be "owned" by just a single table, or may be shared among many tables. When using :class:`_types.Enum` or :class:`_postgresql.ENUM` in an "inline" fashion, the ``CREATE TYPE`` and ``DROP TYPE`` is emitted corresponding to when the :meth:`_schema.Table.create` and :meth:`_schema.Table.drop` methods are called:: table = Table('sometable', metadata, Column('some_enum', ENUM('a', 'b', 'c', name='myenum')) ) table.create(engine) # will emit CREATE ENUM and CREATE TABLE table.drop(engine) # will emit DROP TABLE and DROP ENUM To use a common enumerated type between multiple tables, the best practice is to declare the :class:`_types.Enum` or :class:`_postgresql.ENUM` independently, and associate it with the :class:`_schema.MetaData` object itself:: my_enum = ENUM('a', 'b', 'c', name='myenum', metadata=metadata) t1 = Table('sometable_one', metadata, Column('some_enum', myenum) ) t2 = Table('sometable_two', metadata, Column('some_enum', myenum) ) When this pattern is used, care must still be taken at the level of individual table creates. Emitting CREATE TABLE without also specifying ``checkfirst=True`` will still cause issues:: t1.create(engine) # will fail: no such type 'myenum' If we specify ``checkfirst=True``, the individual table-level create operation will check for the ``ENUM`` and create if not exists:: # will check if enum exists, and emit CREATE TYPE if not t1.create(engine, checkfirst=True) When using a metadata-level ENUM type, the type will always be created and dropped if either the metadata-wide create/drop is called:: metadata.create_all(engine) # will emit CREATE TYPE metadata.drop_all(engine) # will emit DROP TYPE The type can also be created and dropped directly:: my_enum.create(engine) my_enum.drop(engine) .. versionchanged:: 1.0.0 The PostgreSQL :class:`_postgresql.ENUM` type now behaves more strictly with regards to CREATE/DROP. A metadata-level ENUM type will only be created and dropped at the metadata level, not the table level, with the exception of ``table.create(checkfirst=True)``. The ``table.drop()`` call will now emit a DROP TYPE for a table-level enumerated type.