primary key before emitting an INSERT, and merges distinct objects with duplicate primary keys together as they are encountered, which is essentially semi-deterministic at best. This behavior matches what happens already with persistent objects. fixes #3601
scope of a :meth:`.Session.flush` operation that's raising an exception, as has been observed in some MySQL SAVEPOINT cases, prevents the original database exception from being observed when it was emitted during flush, but only on Py2K because Py2K does not support exception chaining; on Py3K the originating exception is chained. As a workaround, a warning is emitted in this specific case showing at least the string message of the original database error before we proceed to raise the rollback-originating exception. fixes #2696
unambiguous tracking of all object lifecycle state transitions in terms of the :class:`.Session` itself, e.g. pending, transient, persistent, detached. The state of the object within each event is also defined. fixes #2677 - Added a new session lifecycle state :term:`deleted`. This new state represents an object that has been deleted from the :term:`persistent` state and will move to the :term:`detached` state once the transaction is committed. This resolves the long-standing issue that objects which were deleted existed in a gray area between persistent and detached. The :attr:`.InstanceState.persistent` accessor will **no longer** report on a deleted object as persistent; the :attr:`.InstanceState.deleted` accessor will instead be True for these objects, until they become detached. - The :paramref:`.Session.weak_identity_map` parameter is deprecated. See the new recipe at :ref:`session_referencing_behavior` for an event-based approach to maintaining strong identity map behavior. references #3517
where we refer to the "weak_identity_map" option, and add additional exposition in the session documentation which refers to it. fixes #3517
:meth:`.Session.begin_nested` operations would fail to propagate the "dirty" flag for an object that had been updated within the inner savepoint, such that if the enclosing savepoint were rolled back, the object would not be part of the state that was expired and therefore reverted to its database state. fixes #3352
commit phase of the session, which without it could cause a "dictionary changed size during iter" error if garbage collection interacted within the process. Change was introduced by
attached to session X" would fail to prevent the object from also being attached to the new session, in the case that execution continued after the error raise occurred. fixes #3301