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Fixed problem with assiging an empty list to m2m related descriptors,…

… introduced in [4231].

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4232 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit e859f108f160ede64d07d248e60a70233b4b4132 1 parent 2d6095e
@freakboy3742 freakboy3742 authored
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40 django/db/models/fields/related.py
@@ -317,25 +317,27 @@ def _add_items(self, source_col_name, target_col_name, *objs):
# *objs - objects to add
from django.db import connection
- # Add the newly created or already existing objects to the join table.
- # First find out which items are already added, to avoid adding them twice
- new_ids = set([obj._get_pk_val() for obj in objs])
- cursor = connection.cursor()
- cursor.execute("SELECT %s FROM %s WHERE %s = %%s AND %s IN (%s)" % \
- (target_col_name, self.join_table, source_col_name,
- target_col_name, ",".join(['%s'] * len(new_ids))),
- [self._pk_val] + list(new_ids))
- if cursor.rowcount is not None and cursor.rowcount != 0:
- existing_ids = set([row[0] for row in cursor.fetchmany(cursor.rowcount)])
- else:
- existing_ids = set()
-
- # Add the ones that aren't there already
- for obj_id in (new_ids - existing_ids):
- cursor.execute("INSERT INTO %s (%s, %s) VALUES (%%s, %%s)" % \
- (self.join_table, source_col_name, target_col_name),
- [self._pk_val, obj_id])
- transaction.commit_unless_managed()
+ # If there aren't any objects, there is nothing to do.
+ if objs:
+ # Add the newly created or already existing objects to the join table.
+ # First find out which items are already added, to avoid adding them twice
+ new_ids = set([obj._get_pk_val() for obj in objs])
+ cursor = connection.cursor()
+ cursor.execute("SELECT %s FROM %s WHERE %s = %%s AND %s IN (%s)" % \
+ (target_col_name, self.join_table, source_col_name,
+ target_col_name, ",".join(['%s'] * len(new_ids))),
+ [self._pk_val] + list(new_ids))
+ if cursor.rowcount is not None and cursor.rowcount != 0:
+ existing_ids = set([row[0] for row in cursor.fetchmany(cursor.rowcount)])
+ else:
+ existing_ids = set()
+
+ # Add the ones that aren't there already
+ for obj_id in (new_ids - existing_ids):
+ cursor.execute("INSERT INTO %s (%s, %s) VALUES (%%s, %%s)" % \
+ (self.join_table, source_col_name, target_col_name),
+ [self._pk_val, obj_id])
+ transaction.commit_unless_managed()
def _remove_items(self, source_col_name, target_col_name, *objs):
# source_col_name: the PK colname in join_table for the source object
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12 tests/modeltests/many_to_many/models.py
@@ -231,4 +231,16 @@ class Meta:
>>> p1.article_set.all()
[<Article: NASA uses Python>]
+# An alternate to calling clear() is to assign the empty set
+>>> p1.article_set = []
+>>> p1.article_set.all()
+[]
+
+>>> a2.publications = [p1, new_publication]
+>>> a2.publications.all()
+[<Publication: Highlights for Children>, <Publication: The Python Journal>]
+>>> a2.publications = []
+>>> a2.publications.all()
+[]
+
"""}
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