- Added new parameter :paramref:`.mapper.confirm_deleted_rows`. Defaults

to True, indicates that a series of DELETE statements should confirm
that the cursor rowcount matches the number of primary keys that should
have matched;  this behavior had been taken off in most cases
(except when version_id is used) to support the unusual edge case of
self-referential ON DELETE CASCADE; to accomodate this, the message
is now just a warning, not an exception, and the flag can be used
to indicate a mapping that expects self-refererntial cascaded
deletes of this nature.  See also :ticket:`2403` for background on the
original change. re: #2403 fix #3007

1 files changed, 17 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 4747c075d..a939cb9c7 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -110,6 +110,7 @@ class Mapper(_InspectionAttr):
                  include_properties=None,
                  exclude_properties=None,
                  passive_updates=True,
+                 confirm_deleted_rows=True,
                  eager_defaults=False,
                  legacy_is_orphan=False,
                  _compiled_cache_size=100,
@@ -208,6 +209,17 @@ class Mapper(_InspectionAttr):
 
            See the section :ref:`concrete_inheritance` for an example.
 
+        :param confirm_deleted_rows: defaults to True; when a DELETE occurs
+          of one more more rows based on specific primary keys, a warning is
+          emitted when the number of rows matched does not equal the number
+          of rows expected.  This parameter may be set to False to handle the case
+          where database ON DELETE CASCADE rules may be deleting some of those
+          rows automatically.  The warning may be changed to an exception
+          in a future release.
+
+          .. versionadded:: 0.9.4 - added :paramref:`.mapper.confirm_deleted_rows`
+             as well as conditional matched row checking on delete.
+
         :param eager_defaults: if True, the ORM will immediately fetch the
           value of server-generated default values after an INSERT or UPDATE,
           rather than leaving them as expired to be fetched on next access.
@@ -545,9 +557,13 @@ class Mapper(_InspectionAttr):
         self._compiled_cache_size = _compiled_cache_size
         self._reconstructor = None
         self._deprecated_extensions = util.to_list(extension or [])
-
         self.allow_partial_pks = allow_partial_pks
 
+        if self.inherits and not self.concrete:
+            self.confirm_deleted_rows = False
+        else:
+            self.confirm_deleted_rows = confirm_deleted_rows
+
         self._set_with_polymorphic(with_polymorphic)
 
         if isinstance(self.local_table, expression.SelectBase):