Fixed #25544 -- Removed duplicate ids in prefetch_related() queries.

django/contrib/postgres/fields/array.py

@@ -5,7 +5,7 @@ from django.contrib.postgres.forms import SimpleArrayField
 from django.contrib.postgres.validators import ArrayMaxLengthValidator
 from django.core import checks, exceptions
 from django.db.models import Field, IntegerField, Transform
-from django.db.models.lookups import Exact
+from django.db.models.lookups import Exact, In
 from django.utils import six
 from django.utils.translation import string_concat, ugettext_lazy as _
 
@@ -217,6 +217,15 @@ class ArrayLenTransform(Transform):
         ) % {'lhs': lhs}, params
 
 
+@ArrayField.register_lookup
+class ArrayInLookup(In):
+    def get_prep_lookup(self):
+        values = super(ArrayInLookup, self).get_prep_lookup()
+        # In.process_rhs() expects values to be hashable, so convert lists
+        # to tuples.
+        return [tuple(value) for value in values]
+
+
 class IndexTransform(Transform):
 
     def __init__(self, index, base_field, *args, **kwargs):

django/db/models/lookups.py

@@ -204,12 +204,17 @@ class In(BuiltinLookup):
 
     def process_rhs(self, compiler, connection):
         if self.rhs_is_direct_value():
-            # rhs should be an iterable, we use batch_process_rhs
+            try:
-            # to prepare/transform those values
+                rhs = set(self.rhs)
-            rhs = list(self.rhs)
+            except TypeError:  # Unhashable items in self.rhs
+                rhs = self.rhs
+
             if not rhs:
                 from django.db.models.sql.datastructures import EmptyResultSet
                 raise EmptyResultSet
+
+            # rhs should be an iterable; use batch_process_rhs() to
+            # prepare/transform those values.
             sqls, sqls_params = self.batch_process_rhs(compiler, connection, rhs)
             placeholder = '(' + ', '.join(sqls) + ')'
             return (placeholder, sqls_params)

tests/postgres_tests/test_hstore.py

@@ -67,6 +67,14 @@ class TestQuerying(PostgreSQLTestCase):
             self.objs[:2]
         )
 
+    def test_in_generator(self):
+        def search():
+            yield {'a': 'b'}
+        self.assertSequenceEqual(
+            HStoreModel.objects.filter(field__in=search()),
+            self.objs[:1]
+        )
+
     def test_has_key(self):
         self.assertSequenceEqual(
             HStoreModel.objects.filter(field__has_key='c'),

tests/prefetch_related/tests.py

@@ -6,6 +6,7 @@ from django.db import connection
 from django.db.models import Prefetch
 from django.db.models.query import get_prefetcher
 from django.test import TestCase, override_settings
+from django.test.utils import CaptureQueriesContext
 from django.utils import six
 from django.utils.encoding import force_text
 
@@ -245,6 +246,27 @@ class PrefetchRelatedTests(TestCase):
         # save of reverse relation assignment.
         self.assertEqual(self.author1.books.count(), 2)
 
+    def test_m2m_then_reverse_fk_object_ids(self):
+        with CaptureQueriesContext(connection) as queries:
+            list(Book.objects.prefetch_related('authors__addresses'))
+
+        sql = queries[-1]['sql']
+        self.assertEqual(sql.count(self.author1.name), 1)
+
+    def test_m2m_then_m2m_object_ids(self):
+        with CaptureQueriesContext(connection) as queries:
+            list(Book.objects.prefetch_related('authors__favorite_authors'))
+
+        sql = queries[-1]['sql']
+        self.assertEqual(sql.count(self.author1.name), 1)
+
+    def test_m2m_then_reverse_one_to_one_object_ids(self):
+        with CaptureQueriesContext(connection) as queries:
+            list(Book.objects.prefetch_related('authors__authorwithage'))
+
+        sql = queries[-1]['sql']
+        self.assertEqual(sql.count(str(self.author1.id)), 1, sql)
+
 
 class CustomPrefetchTests(TestCase):
     @classmethod