title: SQLAlchemy: How to conditionally choose type for column by depending on its backend
body: <p>I want to use <a href="http://docs.sqlalchemy.org/en/rel_0_8/dialects/postgresql.html#sqlalchemy.dialects.postgresql.HSTORE" rel="noreferrer"><code>HSTORE</code></a> type for a column if it uses PostgreSQL as its backend, or <a href="http://docs.sqlalchemy.org/en/rel_0_8/core/types.html#sqlalchemy.types.PickleType" rel="noreferrer"><code>PickleType</code></a> otherwise.  The problem is that we cannot determine which backend will be used when schema is being defined (in Python). How can I determine this and conditionally choose the data type when the table actually is created on the backend database?</p>