Fixed #16891 -- Made Model/QuerySet.delete() return the number of deleted objects.

9 files changed, 120 insertions, 20 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 27764bba84..b679d08654 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -833,7 +833,7 @@ class Model(six.with_metaclass(ModelBase)):
 
         collector = Collector(using=using)
         collector.collect([self], keep_parents=keep_parents)
-        collector.delete()
+        return collector.delete()
 
     delete.alters_data = True
 
diff --git a/django/db/models/deletion.py b/django/db/models/deletion.py
index 8bfba43fac..61263b569e 100644
--- a/django/db/models/deletion.py
+++ b/django/db/models/deletion.py
@@ -1,4 +1,4 @@
-from collections import OrderedDict
+from collections import Counter, OrderedDict
 from itertools import chain
 from operator import attrgetter
 
@@ -280,6 +280,8 @@ class Collector(object):
         # don't support transactions or cannot defer constraint checks until the
         # end of a transaction.
         self.sort()
+        # number of objects deleted for each model label
+        deleted_counter = Counter()
 
         with transaction.atomic(using=self.using, savepoint=False):
             # send pre_delete signals
@@ -291,7 +293,8 @@ class Collector(object):
 
             # fast deletes
             for qs in self.fast_deletes:
-                qs._raw_delete(using=self.using)
+                count = qs._raw_delete(using=self.using)
+                deleted_counter[qs.model._meta.label] += count
 
             # update fields
             for model, instances_for_fieldvalues in six.iteritems(self.field_updates):
@@ -308,7 +311,8 @@ class Collector(object):
             for model, instances in six.iteritems(self.data):
                 query = sql.DeleteQuery(model)
                 pk_list = [obj.pk for obj in instances]
-                query.delete_batch(pk_list, self.using)
+                count = query.delete_batch(pk_list, self.using)
+                deleted_counter[model._meta.label] += count
 
                 if not model._meta.auto_created:
                     for obj in instances:
@@ -324,3 +328,4 @@ class Collector(object):
         for model, instances in six.iteritems(self.data):
             for instance in instances:
                 setattr(instance, model._meta.pk.attname, None)
+        return sum(deleted_counter.values()), dict(deleted_counter)
diff --git a/django/db/models/query.py b/django/db/models/query.py
index 050994811a..343f4dc718 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -590,10 +590,12 @@ class QuerySet(object):
 
         collector = Collector(using=del_query.db)
         collector.collect(del_query)
-        collector.delete()
+        deleted, _rows_count = collector.delete()
 
         # Clear the result cache, in case this QuerySet gets reused.
         self._result_cache = None
+        return deleted, _rows_count
+
     delete.alters_data = True
     delete.queryset_only = True
 
@@ -602,7 +604,7 @@ class QuerySet(object):
         Deletes objects found from the given queryset in single direct SQL
         query. No signals are sent, and there is no protection for cascades.
         """
-        sql.DeleteQuery(self.model).delete_qs(self, using)
+        return sql.DeleteQuery(self.model).delete_qs(self, using)
     _raw_delete.alters_data = True
 
     def update(self, **kwargs):
diff --git a/django/db/models/sql/subqueries.py b/django/db/models/sql/subqueries.py
index 14739dea0e..2dbdf2edd7 100644
--- a/django/db/models/sql/subqueries.py
+++ b/django/db/models/sql/subqueries.py
@@ -5,7 +5,9 @@ Query subclasses which provide extra functionality beyond simple data retrieval.
 from django.core.exceptions import FieldError
 from django.db import connections
 from django.db.models.query_utils import Q
-from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, NO_RESULTS
+from django.db.models.sql.constants import (
+    CURSOR, GET_ITERATOR_CHUNK_SIZE, NO_RESULTS,
+)
 from django.db.models.sql.query import Query
 from django.utils import six
 
@@ -23,7 +25,8 @@ class DeleteQuery(Query):
     def do_query(self, table, where, using):
         self.tables = [table]
         self.where = where
-        self.get_compiler(using).execute_sql(NO_RESULTS)
+        cursor = self.get_compiler(using).execute_sql(CURSOR)
+        return cursor.rowcount if cursor else 0
 
     def delete_batch(self, pk_list, using, field=None):
         """
@@ -32,13 +35,16 @@ class DeleteQuery(Query):
         More than one physical query may be executed if there are a
         lot of values in pk_list.
         """
+        # number of objects deleted
+        num_deleted = 0
         if not field:
             field = self.get_meta().pk
         for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
             self.where = self.where_class()
             self.add_q(Q(
                 **{field.attname + '__in': pk_list[offset:offset + GET_ITERATOR_CHUNK_SIZE]}))
-            self.do_query(self.get_meta().db_table, self.where, using=using)
+            num_deleted += self.do_query(self.get_meta().db_table, self.where, using=using)
+        return num_deleted
 
     def delete_qs(self, query, using):
         """
@@ -63,8 +69,7 @@ class DeleteQuery(Query):
                 values = list(query.values_list('pk', flat=True))
                 if not values:
                     return
-                self.delete_batch(values, using)
-                return
+                return self.delete_batch(values, using)
             else:
                 innerq.clear_select_clause()
                 innerq.select = [
@@ -73,7 +78,8 @@ class DeleteQuery(Query):
                 values = innerq
             self.where = self.where_class()
             self.add_q(Q(pk__in=values))
-        self.get_compiler(using).execute_sql(NO_RESULTS)
+        cursor = self.get_compiler(using).execute_sql(CURSOR)
+        return cursor.rowcount if cursor else 0
 
 
 class UpdateQuery(Query):
diff --git a/docs/ref/models/instances.txt b/docs/ref/models/instances.txt
index 02903668d1..6af5ae3caa 100644
--- a/docs/ref/models/instances.txt
+++ b/docs/ref/models/instances.txt
@@ -537,7 +537,8 @@ Deleting objects
 
 Issues an SQL ``DELETE`` for the object. This only deletes the object in the
 database; the Python instance will still exist and will still have data in
-its fields.
+its fields. This method returns the number of objects deleted and a dictionary
+with the number of deletions per object type.
 
 For more details, including how to delete objects in bulk, see
 :ref:`topics-db-queries-delete`.
@@ -553,6 +554,10 @@ keep the parent model's data.
 
     The ``keep_parents`` parameter was added.
 
+.. versionchanged:: 1.9
+
+    The return value describing the number of objects deleted was added.
+
 Pickling objects
 ================
 
diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt
index 510fbcbbb8..100553bd87 100644
--- a/docs/ref/models/querysets.txt
+++ b/docs/ref/models/querysets.txt
@@ -2070,8 +2070,11 @@ delete
 
 .. method:: delete()
 
-Performs an SQL delete query on all rows in the :class:`.QuerySet`. The
-``delete()`` is applied instantly. You cannot call ``delete()`` on a
+Performs an SQL delete query on all rows in the :class:`.QuerySet` and
+returns the number of objects deleted and a dictionary with the number of
+deletions per object type.
+
+The ``delete()`` is applied instantly. You cannot call ``delete()`` on a
 :class:`.QuerySet` that has had a slice taken or can otherwise no longer be
 filtered.
 
@@ -2081,15 +2084,22 @@ For example, to delete all the entries in a particular blog::
 
     # Delete all the entries belonging to this Blog.
     >>> Entry.objects.filter(blog=b).delete()
+    (4, {'weblog.Entry': 2, 'weblog.Entry_authors': 2})
+
+.. versionchanged:: 1.9
+
+    The return value describing the number of objects deleted was added.
 
 By default, Django's :class:`~django.db.models.ForeignKey` emulates the SQL
 constraint ``ON DELETE CASCADE`` — in other words, any objects with foreign
 keys pointing at the objects to be deleted will be deleted along with them.
 For example::
 
-    blogs = Blog.objects.all()
+    >>> blogs = Blog.objects.all()
+
     # This will delete all Blogs and all of their Entry objects.
-    blogs.delete()
+    >>> blogs.delete()
+    (5, {'weblog.Blog': 1, 'weblog.Entry': 2, 'weblog.Entry_authors': 2})
 
 This cascade behavior is customizable via the
 :attr:`~django.db.models.ForeignKey.on_delete` argument to the
diff --git a/docs/releases/1.9.txt b/docs/releases/1.9.txt
index 1aff56aef3..e36c4512ca 100644
--- a/docs/releases/1.9.txt
+++ b/docs/releases/1.9.txt
@@ -214,6 +214,10 @@ Models
   <django.db.models.Model.delete>` to allow deleting only a child's data in a
   model that uses multi-table inheritance.
 
+* :meth:`Model.delete() <django.db.models.Model.delete>`
+  and :meth:`QuerySet.delete() <django.db.models.query.QuerySet.delete>` return
+  the number of objects deleted.
+
 * Added a system check to prevent defining both ``Meta.ordering`` and
   ``order_with_respect_to`` on the same model.
 
diff --git a/docs/topics/db/queries.txt b/docs/topics/db/queries.txt
index 8bb2bab482..28ddf660df 100644
--- a/docs/topics/db/queries.txt
+++ b/docs/topics/db/queries.txt
@@ -899,9 +899,15 @@ Deleting objects
 
 The delete method, conveniently, is named
 :meth:`~django.db.models.Model.delete`. This method immediately deletes the
-object and has no return value. Example::
+object and returns the number of objects deleted and a dictionary with
+the number of deletions per object type. Example::
 
-    e.delete()
+    >>> e.delete()
+    (1, {'weblog.Entry': 1})
+
+.. versionchanged:: 1.9
+
+    The return value describing the number of objects deleted was added.
 
 You can also delete objects in bulk. Every
 :class:`~django.db.models.query.QuerySet` has a
@@ -911,7 +917,8 @@ members of that :class:`~django.db.models.query.QuerySet`.
 For example, this deletes all ``Entry`` objects with a ``pub_date`` year of
 2005::
 
-    Entry.objects.filter(pub_date__year=2005).delete()
+    >>> Entry.objects.filter(pub_date__year=2005).delete()
+    (5, {'webapp.Entry': 5})
 
 Keep in mind that this will, whenever possible, be executed purely in SQL, and
 so the ``delete()`` methods of individual object instances will not necessarily
@@ -923,6 +930,10 @@ object individually) rather than using the bulk
 :meth:`~django.db.models.query.QuerySet.delete` method of a
 :class:`~django.db.models.query.QuerySet`.
 
+.. versionchanged:: 1.9
+
+    The return value describing the number of objects deleted was added.
+
 When Django deletes an object, by default it emulates the behavior of the SQL
 constraint ``ON DELETE CASCADE`` -- in other words, any objects which had
 foreign keys pointing at the object to be deleted will be deleted along with
diff --git a/tests/delete/tests.py b/tests/delete/tests.py
index dd3c427824..11e780bfac 100644
--- a/tests/delete/tests.py
+++ b/tests/delete/tests.py
@@ -137,6 +137,7 @@ class OnDeleteTests(TestCase):
 
 
 class DeletionTests(TestCase):
+
     def test_m2m(self):
         m = M.objects.create()
         r = R.objects.create()
@@ -356,6 +357,62 @@ class DeletionTests(TestCase):
         self.assertFalse(RChild.objects.filter(id=child.id).exists())
         self.assertTrue(R.objects.filter(id=parent_id).exists())
 
+    def test_queryset_delete_returns_num_rows(self):
+        """
+        QuerySet.delete() should return the number of deleted rows and a
+        dictionary with the number of deletions for each object type.
+        """
+        Avatar.objects.bulk_create([Avatar(desc='a'), Avatar(desc='b'), Avatar(desc='c')])
+        avatars_count = Avatar.objects.count()
+        deleted, rows_count = Avatar.objects.all().delete()
+        self.assertEqual(deleted, avatars_count)
+
+        # more complex example with multiple object types
+        r = R.objects.create()
+        h1 = HiddenUser.objects.create(r=r)
+        HiddenUser.objects.create(r=r)
+        HiddenUserProfile.objects.create(user=h1)
+        existed_objs = {
+            R._meta.label: R.objects.count(),
+            HiddenUser._meta.label: HiddenUser.objects.count(),
+            A._meta.label: A.objects.count(),
+            MR._meta.label: MR.objects.count(),
+            HiddenUserProfile._meta.label: HiddenUserProfile.objects.count(),
+        }
+        deleted, deleted_objs = R.objects.all().delete()
+        for k, v in existed_objs.items():
+            self.assertEqual(deleted_objs[k], v)
+
+    def test_model_delete_returns_num_rows(self):
+        """
+        Model.delete() should return the number of deleted rows and a
+        dictionary with the number of deletions for each object type.
+        """
+        r = R.objects.create()
+        h1 = HiddenUser.objects.create(r=r)
+        h2 = HiddenUser.objects.create(r=r)
+        HiddenUser.objects.create(r=r)
+        HiddenUserProfile.objects.create(user=h1)
+        HiddenUserProfile.objects.create(user=h2)
+        m1 = M.objects.create()
+        m2 = M.objects.create()
+        MR.objects.create(r=r, m=m1)
+        r.m_set.add(m1)
+        r.m_set.add(m2)
+        r.save()
+        existed_objs = {
+            R._meta.label: R.objects.count(),
+            HiddenUser._meta.label: HiddenUser.objects.count(),
+            A._meta.label: A.objects.count(),
+            MR._meta.label: MR.objects.count(),
+            HiddenUserProfile._meta.label: HiddenUserProfile.objects.count(),
+            M.m2m.through._meta.label: M.m2m.through.objects.count(),
+        }
+        deleted, deleted_objs = r.delete()
+        self.assertEqual(deleted, sum(existed_objs.values()))
+        for k, v in existed_objs.items():
+            self.assertEqual(deleted_objs[k], v)
+
 
 class FastDeleteTests(TestCase):