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

2 files changed, 18 insertions, 4 deletions

diff --git a/django/contrib/postgres/fields/array.py b/django/contrib/postgres/fields/array.py
index 65f28672aa..9a1e3c286b 100644
--- a/django/contrib/postgres/fields/array.py
+++ b/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):
diff --git a/django/db/models/lookups.py b/django/db/models/lookups.py
index 7b4862a46c..045f7d194f 100644
--- a/django/db/models/lookups.py
+++ b/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
-            # to prepare/transform those values
-            rhs = list(self.rhs)
+            try:
+                rhs = set(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)