Fixed #11881 -- removed junk from aggregation subqueries

There were clauses that weren't needed in the subqueries. These were
ORDER BY, SELECT FOR UPDATE and related selections.

django/db/models/sql/query.py

@@ -330,8 +330,16 @@ class Query(object):
             from django.db.models.sql.subqueries import AggregateQuery
             query = AggregateQuery(self.model)
             obj = self.clone()
-            relabels = dict((t, 'subquery') for t in self.tables)
+            if not force_subq:
+                # In forced subq case the ordering and limits will likely
+                # affect the results.
+                obj.clear_ordering(True)
+                obj.clear_limits()
+            obj.select_for_update = False
+            obj.select_related = False
+            obj.related_select_cols = []
 
+            relabels = dict((t, 'subquery') for t in self.tables)
             # Remove any aggregates marked for reduction from the subquery
             # and move them to the outer AggregateQuery.
             for alias, aggregate in self.aggregate_select.items():

tests/aggregation/tests.py

@@ -3,8 +3,10 @@ from __future__ import unicode_literals
 import datetime
 from decimal import Decimal
 
+from django.db import connection
 from django.db.models import Avg, Sum, Count, Max, Min
 from django.test import TestCase, Approximate
+from django.test.utils import CaptureQueriesContext
 
 from .models import Author, Publisher, Book, Store
 
@@ -625,3 +627,18 @@ class BaseAggregateTestCase(TestCase):
         qs = Book.objects.all().order_by('-rating')[0:3]
         vals = qs.aggregate(average_top3_rating=Avg('rating'))['average_top3_rating']
         self.assertAlmostEqual(vals, 4.5, places=2)
+
+    def test_ticket11881(self):
+        """
+        Check that subqueries do not needlessly contain ORDER BY, SELECT FOR UPDATE
+        or select_related() stuff.
+        """
+        qs = Book.objects.all().select_for_update().order_by(
+            'pk').select_related('publisher').annotate(max_pk=Max('pk'))
+        with CaptureQueriesContext(connection) as captured_queries:
+            qs.aggregate(avg_pk=Avg('max_pk'))
+            self.assertEqual(len(captured_queries), 1)
+            qstr = captured_queries[0]['sql'].lower()
+            self.assertNotIn('for update', qstr)
+            self.assertNotIn('order by', qstr)
+            self.assertEqual(qstr.count(' join '), 0)