Serializer/Deserializer objects for usage with SQLAlchemy query structures, allowing “contextual” deserialization.
Any SQLAlchemy query structure, either based on sqlalchemy.sql.* or sqlalchemy.orm.* can be used. The mappers, Tables, Columns, Session etc. which are referenced by the structure are not persisted in serialized form, but are instead re-associated with the query structure when it is deserialized.
Usage is nearly the same as that of the standard Python pickle module:
from sqlalchemy.ext.serializer import loads, dumps metadata = MetaData(bind=some_engine) Session = scoped_session(sessionmaker()) # ... define mappers query = Session.query(MyClass).filter(MyClass.somedata=='foo').order_by(MyClass.sortkey) # pickle the query serialized = dumps(query) # unpickle. Pass in metadata + scoped_session query2 = loads(serialized, metadata, Session) print query2.all()
Similar restrictions as when using raw pickle apply; mapped classes must be themselves be pickleable, meaning they are importable from a module-level namespace.
The serializer module is only appropriate for query structures. It is not needed for: