SQLAlchemy: How to conditionally choose type for column by depending on its backend

Question

I want to use HSTORE type for a column if it uses PostgreSQL as its backend, or PickleType otherwise. The problem is that we cannot determine which backend will be used when sc

Answer 1

You can accomplish something like this with TypeEngine.with_variant:

from sqlalchemy.types import PickleType
from sqlalchemy.dialects import postgresql

HybridType = PickleType()

HybridType = HybridType.with_variant(postgresql.HSTORE(), 'postgresql')

This creates a new type, HybridType, which you can use like any other type, with the caveat that it will produce an HSTORE column on Postgres and a PickleType everywhere else.