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| author | jonathan vanasco <jonathan@2xlp.com> | 2021-09-24 14:55:59 -0400 |
|---|---|---|
| committer | Jonathan Vanasco <jonathan@2xlp.com> | 2021-10-26 16:42:06 +0000 |
| commit | f3e0bef712da7a40ead247994413b36e5e3dd97b (patch) | |
| tree | 2f038f1efbff361eac417e92c48451cf3a7dd546 | |
| parent | 7cf3e79991b3d00d53bfb98cfdab267b67a5cdda (diff) | |
| download | sqlalchemy-f3e0bef712da7a40ead247994413b36e5e3dd97b.tar.gz | |
Fixes: #4100
Add a warning, in two places, stating `with_for_update` will lock joinedload
tables, because at least one person did not expect the obvious to happen.
Also warn that eager loading techniques may not work with `with_for_update`
and combining the two is not officially supported or recommended.
Change-Id: Iedd609b56b3144d90a90fc2eea3cf5335a2d178a
| -rw-r--r-- | doc/build/orm/loading_relationships.rst | 10 | ||||
| -rw-r--r-- | lib/sqlalchemy/orm/query.py | 9 |
2 files changed, 19 insertions, 0 deletions
diff --git a/doc/build/orm/loading_relationships.rst b/doc/build/orm/loading_relationships.rst index 2734e6870..5a1d5151d 100644 --- a/doc/build/orm/loading_relationships.rst +++ b/doc/build/orm/loading_relationships.rst @@ -444,6 +444,16 @@ On older versions of SQLite, the above nested right JOIN may be re-rendered as a nested subquery. Older versions of SQLAlchemy would convert right-nested joins into subqueries in all cases. + .. warning:: + + Using ``with_for_update`` in the context of eager loading + relationships is not officially supported or recommended by + SQLAlchemy and may not work with certain queries on various + database backends. When ``with_for_update`` is successfully used + with a query that involves :func:`_orm.joinedload`, SQLAlchemy will + attempt to emit SQL that locks all involved tables. + + Joined eager loading and result set batching ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py index fcb9dae57..48f4b9464 100644 --- a/lib/sqlalchemy/orm/query.py +++ b/lib/sqlalchemy/orm/query.py @@ -1602,6 +1602,15 @@ class Query( SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT + .. warning:: + + Using ``with_for_update`` in the context of eager loading + relationships is not officially supported or recommended by + SQLAlchemy and may not work with certain queries on various + database backends. When ``with_for_update`` is successfully used + with a query that involves :func:`_orm.joinedload`, SQLAlchemy will + attempt to emit SQL that locks all involved tables. + .. note:: It is generally a good idea to combine the use of the :meth:`_orm.Query.populate_existing` method when using the :meth:`_orm.Query.with_for_update` method. The purpose of |