- added 'passive_deletes="all"' flag to relation(), disables all

  nulling-out of foreign key attributes during a flush where the parent
  object is deleted.

- fix to FK compile fix from yesterday

4 files changed, 24 insertions, 11 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
diff --git a/lib/sqlalchemy/orm/dependency.py b/lib/sqlalchemy/orm/dependency.py
index 3b837d275..1e461e6bf 100644
--- a/lib/sqlalchemy/orm/dependency.py
+++ b/lib/sqlalchemy/orm/dependency.py
@@ -188,7 +188,7 @@ class OneToManyDP(DependencyProcessor):
             # the child objects have to have their foreign key to the parent set to NULL
             # this phase can be called safely for any cascade but is unnecessary if delete cascade
             # is on.
-            if not self.cascade.delete or self.post_update:
+            if (not self.cascade.delete or self.post_update) and not self.passive_deletes=='all':
                 for obj in deplist:
                     childlist = self.get_object_dependencies(obj, uowcommit, passive=self.passive_deletes)
                     if childlist is not None:
@@ -217,7 +217,7 @@ class OneToManyDP(DependencyProcessor):
         if delete:
             # head object is being deleted, and we manage its list of child objects
             # the child objects have to have their foreign key to the parent set to NULL
-            if not self.post_update and not self.cascade.delete:
+            if not self.post_update and not self.cascade.delete and not self.passive_deletes=='all':
                 for obj in deplist:
                     childlist = self.get_object_dependencies(obj, uowcommit, passive=self.passive_deletes)
                     if childlist is not None:
@@ -265,7 +265,7 @@ class ManyToOneDP(DependencyProcessor):
     def process_dependencies(self, task, deplist, uowcommit, delete = False):
         #print self.mapper.mapped_table.name + " " + self.key + " " + repr(len(deplist)) + " process_dep isdelete " + repr(delete) + " direction " + repr(self.direction)
         if delete:
-            if self.post_update and not self.cascade.delete_orphan:
+            if self.post_update and not self.cascade.delete_orphan and not self.passive_deletes=='all':
                 # post_update means we have to update our row to not reference the child object
                 # before we can DELETE the row
                 for obj in deplist:
diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index 20cbcb235..90a7ba3a4 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -161,6 +161,9 @@ class PropertyLoader(StrategizedProperty):
                 self.cascade = mapperutil.CascadeOptions("all, delete-orphan")
             else:
                 self.cascade = mapperutil.CascadeOptions("save-update, merge")
+        
+        if self.passive_deletes == 'all' and ("delete" in self.cascade or "delete-orphan" in self.cascade):
+            raise exceptions.ArgumentError("Can't set passive_deletes='all' in conjunction with 'delete' or 'delete-orphan' cascade")
 
         self.association = association
         if association:
diff --git a/lib/sqlalchemy/schema.py b/lib/sqlalchemy/schema.py
index 212fdac82..3b7f08f79 100644
--- a/lib/sqlalchemy/schema.py
+++ b/lib/sqlalchemy/schema.py
@@ -509,6 +509,8 @@ class Column(SchemaItem, expression._ColumnClause):
         if not self._is_oid:
             self._pre_existing_column = table._columns.get(self.key)
             table._columns.add(self)
+        else:
+            self._pre_existing_column = None
         if self.primary_key:
             table.primary_key.add(self)
         elif self.key in table.primary_key:
@@ -555,6 +557,7 @@ class Column(SchemaItem, expression._ColumnClause):
         c.orig_set = self.orig_set
         c.__originating_column = self.__originating_column
         c._distance = self._distance + 1
+        c._pre_existing_column = self._pre_existing_column
         if not c._is_oid:
             selectable.columns.add(c)
             if self.primary_key: