How to use Enum with SQLAlchemy and Alembic?

Why real values in DB are ‘DRAFT’, ‘APPROVE’, ‘PUBLISHED’, but not draft, etc? I supposed there should be ENUM values, not names.

As Peter Bašista’s already mentioned SQLAlchemy uses the enum names (DRAFT, APPROVE, PUBLISHED) in the database. I assume that was done because the enum values (“draft”, “approve”, …) can be arbitrary types in Python and they are not guaranteed to be unique (unless @unique is used).

However since SQLAlchemy 1.2.3 the Enum class accepts a parameter values_callable which can be used to store enum values in the database:

    status = db.Column(
        db.Enum(PostStatus, values_callable=lambda obj: [e.value for e in obj]),
        nullable=False,
        default=PostStatus.DRAFT.value,
        server_default=PostStatus.DRAFT.value
    )

Why type poststatus was not created on DB-level automatically? In the similar migration it was.

I think basically you are hitting a limitation of alembic: It won’t handle enums on PostgreSQL correctly in some cases. I suspect the main issue in your case is Autogenerate doesn’t correctly handle postgresql enums #278.

I noticed that the type is created correctly if I use alembic.op.create_table so my workaround is basically:

enum_type = SQLEnum(PostStatus, values_callable=lambda enum: [e.value for e in enum])
op.create_table(
    '_dummy',
    sa.Column('id', Integer, primary_key=True),
    sa.Column('status', enum_type)
)
op.drop_table('_dummy')
c_status = Column('status', enum_type, nullable=False)
add_column('posts', c_status)