diff options
Diffstat (limited to 'lib/sqlalchemy/orm/__init__.py')
| -rw-r--r-- | lib/sqlalchemy/orm/__init__.py | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/lib/sqlalchemy/orm/__init__.py b/lib/sqlalchemy/orm/__init__.py index 0d4dec4bc..5a2c41449 100644 --- a/lib/sqlalchemy/orm/__init__.py +++ b/lib/sqlalchemy/orm/__init__.py @@ -168,14 +168,21 @@ def relation(argument, secondary=None, **kwargs): indicates the ordering that should be applied when loading these items. passive_deletes=False - Indicates if lazy-loaders should not be executed during the ``flush()`` - process, which normally occurs in order to locate all existing child - items when a parent item is to be deleted. Setting this flag to True is - appropriate when ``ON DELETE CASCADE`` rules have been set up on the - actual tables so that the database may handle cascading deletes - automatically. This strategy is useful particularly for handling the - deletion of objects that have very large (and/or deep) child-object - collections. + Indicates the behavior of delete operations. + A value of True indicates that unloaded child items should not be loaded + during a delete operation on the parent. Normally, when a parent + item is deleted, all child items are loaded so that they can either be + marked as deleted, or have their foreign key to the parent set to NULL. + Marking this flag as True usually implies an ON DELETE <CASCADE|SET NULL> + rule is in place which will handle updating/deleting child rows on the + database side. + + Additionally, setting the flag to the string value 'all' will disable + the "nulling out" of the child foreign keys, when there is no delete or + delete-orphan cascade enabled. This is typically used when a triggering + or error raise scenario is in place on the database side. Note that + the foreign key attributes on in-session child objects will not be changed + after a flush occurs so this is a very special use-case setting. post_update this indicates that the relationship should be handled by a second |