Fixed #31792 -- Made Exists() reuse QuerySet.exists() optimizations.

The latter is already optimized to limit the number of results, avoid
selecting unnecessary fields, and drop ordering if possible without
altering the semantic of the query.

1 files changed, 7 insertions, 1 deletions

diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 659fa87314..4648daf395 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -522,7 +522,7 @@ class Query(BaseExpression):
     def has_filters(self):
         return self.where
 
-    def has_results(self, using):
+    def exists(self):
         q = self.clone()
         if not q.distinct:
             if q.group_by is True:
@@ -533,6 +533,12 @@ class Query(BaseExpression):
             q.clear_select_clause()
         q.clear_ordering(True)
         q.set_limits(high=1)
+        q.add_extra({'a': 1}, None, None, None, None, None)
+        q.set_extra_mask(['a'])
+        return q
+
+    def has_results(self, using):
+        q = self.exists()
         compiler = q.get_compiler(using=using)
         return compiler.has_results()