From eb4724a0632928bda2a512a9117a91260096e457 Mon Sep 17 00:00:00 2001
From: Simon Charette <charettes@users.noreply.github.com>
Date: Fri, 28 Apr 2017 09:30:35 -0400
Subject: [PATCH] Reverted "Refs #20939 -- Moved subquery ordering clearing
 optimization to the __in lookup."

This reverts commit e62ea0bb9cbb54c1eef848871fe3eab2bad268dc since it
broke multi-column __in lookups and _meta.order_wrt on Oracle.
---
 django/db/models/lookups.py   | 15 +++------------
 django/db/models/sql/query.py |  6 ++++++
 2 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/django/db/models/lookups.py b/django/db/models/lookups.py
index 78ed3e477f..48e68d0b8b 100644
--- a/django/db/models/lookups.py
+++ b/django/db/models/lookups.py
@@ -367,18 +367,9 @@ class In(FieldGetDbPrepValueIterableMixin, BuiltinLookup):
             placeholder = '(' + ', '.join(sqls) + ')'
             return (placeholder, sqls_params)
         else:
-            from django.db.models.sql.query import Query  # avoid circular import
-            if isinstance(self.rhs, Query):
-                query = self.rhs
-                # It's safe to drop ordering if the queryset isn't using
-                # slicing, distinct(*fields), or select_for_update().
-                if (query.low_mark == 0 and query.high_mark is None and
-                        not query.distinct_fields and
-                        not query.select_for_update):
-                    query.clear_ordering(True)
-                if not query.has_select_fields:
-                    query.clear_select_clause()
-                    query.add_fields(['pk'])
+            if not getattr(self.rhs, 'has_select_fields', True):
+                self.rhs.clear_select_clause()
+                self.rhs.add_fields(['pk'])
             return super().process_rhs(compiler, connection)
 
     def get_rhs_op(self, connection, rhs):
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index c8cb095d09..a1c1c4be38 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -981,6 +981,12 @@ class Query:
         # Subqueries need to use a different set of aliases than the outer query.
         clone.bump_prefix(query)
         clone.subquery = True
+        # It's safe to drop ordering if the queryset isn't using slicing,
+        # distinct(*fields) or select_for_update().
+        if (self.low_mark == 0 and self.high_mark is None and
+                not self.distinct_fields and
+                not self.select_for_update):
+            clone.clear_ordering(True)
         return clone
 
     def prepare_lookup_value(self, value, lookups, can_reuse, allow_joins=True):