:func:`.validates` function; when set to False, a validation event will not be triggered if the event was initated as a backref to an attribute operation from the other side. [ticket:1535] - break out validation tests into an updated module test_validators
version id programmatically outside of the generator. using this system, we can also leave the version id alone.
to rely upon server generated version identifiers, using triggers or other database-provided versioning features, by passing the value ``False``. The ORM will use RETURNING when available to immediately load the new version identifier, else it will emit a second SELECT. [ticket:2793] - The ``eager_defaults`` flag of :class:`.Mapper` will now allow the newly generated default values to be fetched using an inline RETURNING clause, rather than a second SELECT statement, for backends that support RETURNING. - Added a new variant to :meth:`.ValuesBase.returning` called :meth:`.ValuesBase.return_defaults`; this allows arbitrary columns to be added to the RETURNING clause of the statement without interfering with the compilers usual "implicit returning" feature, which is used to efficiently fetch newly generated primary key values. For supporting backends, a dictionary of all fetched values is present at :attr:`.ResultProxy.returned_defaults`. - add a glossary entry for RETURNING - add documentation for version id generation, [ticket:867]
- rework the event system so that event modules load after their targets, dependencies are reversed - create an improved strategy lookup system for the ORM - rework the ORM to have very few import cycles - move out "importlater" to just util.dependency - other tricks to cross-populate modules in as clear a way as possible
the import structure of many core modules. ``sqlalchemy.schema`` and ``sqlalchemy.types`` remain in the top-level package, but are now just lists of names that pull from within ``sqlalchemy.sql``. Their implementations are now broken out among ``sqlalchemy.sql.type_api``, ``sqlalchemy.sql.sqltypes``, ``sqlalchemy.sql.schema`` and ``sqlalchemy.sql.ddl``, the last of which was moved from ``sqlalchemy.engine``. ``sqlalchemy.sql.expression`` is also a namespace now which pulls implementations mostly from ``sqlalchemy.sql.elements``, ``sqlalchemy.sql.selectable``, and ``sqlalchemy.sql.dml``. Most of the "factory" functions used to create SQL expression objects have been moved to classmethods or constructors, which are exposed in ``sqlalchemy.sql.expression`` using a programmatic system. Care has been taken such that all the original import namespaces remain intact and there should be no impact on any existing applications. The rationale here was to break out these very large modules into smaller ones, provide more manageable lists of function names, to greatly reduce "import cycles" and clarify the up-front importing of names, and to remove the need for redundant functions and documentation throughout the expression package.