diff --git a/django/db/backends/mysql/compiler.py b/django/db/backends/mysql/compiler.py
index bd4105ff8e..012bca5da6 100644
--- a/django/db/backends/mysql/compiler.py
+++ b/django/db/backends/mysql/compiler.py
@@ -3,7 +3,7 @@ from django.db.models.sql import compiler
 class SQLCompiler(compiler.SQLCompiler):
     def resolve_columns(self, row, fields=()):
         values = []
-        index_extra_select = len(self.query.extra_select.keys())
+        index_extra_select = len(self.query.extra_select)
         for value, field in map(None, row[index_extra_select:], fields):
             if (field and field.get_internal_type() in ("BooleanField", "NullBooleanField") and
                 value in (0, 1)):
diff --git a/django/db/backends/oracle/compiler.py b/django/db/backends/oracle/compiler.py
index c7b10429c2..e21f867f82 100644
--- a/django/db/backends/oracle/compiler.py
+++ b/django/db/backends/oracle/compiler.py
@@ -10,7 +10,7 @@ class SQLCompiler(compiler.SQLCompiler):
             rn_offset = 1
         else:
             rn_offset = 0
-        index_start = rn_offset + len(self.query.extra_select.keys())
+        index_start = rn_offset + len(self.query.extra_select)
         values = [self.query.convert_values(v, None, connection=self.connection)
                   for v in row[rn_offset:index_start]]
         for value, field in map(None, row[index_start:], fields):
diff --git a/django/db/models/base.py b/django/db/models/base.py
index 1e1a138714..157b74ae49 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -779,7 +779,7 @@ class Model(six.with_metaclass(ModelBase, object)):
                 lookup_kwargs[str(field_name)] = lookup_value
 
             # some fields were skipped, no reason to do the check
-            if len(unique_check) != len(lookup_kwargs.keys()):
+            if len(unique_check) != len(lookup_kwargs):
                 continue
 
             qs = model_class._default_manager.filter(**lookup_kwargs)
diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index 1311ea546c..3dc0c6ece4 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -786,7 +786,7 @@ class SQLCompiler(object):
                     row = self.resolve_columns(row, fields)
 
                 if has_aggregate_select:
-                    aggregate_start = len(self.query.extra_select.keys()) + len(self.query.select)
+                    aggregate_start = len(self.query.extra_select) + len(self.query.select)
                     aggregate_end = aggregate_start + len(self.query.aggregate_select)
                     row = tuple(row[:aggregate_start]) + tuple([
                         self.query.resolve_aggregate(value, aggregate, self.connection)