- Fixed a regression introduced by :ticket:`2818` where the EXISTS

query being generated would produce a "columns being replaced"
warning for a statement with two same-named columns,
as the internal SELECT wouldn't have use_labels set.

3 files changed, 27 insertions, 5 deletions

diff --git a/doc/build/changelog/changelog_08.rst b/doc/build/changelog/changelog_08.rst
index 77e70c88a..0e5e788e0 100644
--- a/doc/build/changelog/changelog_08.rst
+++ b/doc/build/changelog/changelog_08.rst
@@ -11,6 +11,16 @@
     :version: 0.8.4
 
     .. change::
+        :tags: bug, orm
+        :tickets: 2818
+        :versions: 0.9.0b2
+
+        Fixed a regression introduced by :ticket:`2818` where the EXISTS
+        query being generated would produce a "columns being replaced"
+        warning for a statement with two same-named columns,
+        as the internal SELECT wouldn't have use_labels set.
+
+    .. change::
         :tags: bug, postgresql
         :tickets: 2855
         :versions: 0.9.0b2
diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 3df12c0a7..c9e7d444b 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -2485,7 +2485,7 @@ class Query(object):
         .. versionadded:: 0.8.1
 
         """
-        return sql.exists(self.statement.with_only_columns(['1']))
+        return sql.exists(self.with_labels().statement.with_only_columns(['1']))
 
     def count(self):
         """Return a count of rows this Query would return.
diff --git a/test/orm/test_query.py b/test/orm/test_query.py
index e9d0f3a7e..63e3c4bb9 100644
--- a/test/orm/test_query.py
+++ b/test/orm/test_query.py
@@ -1726,6 +1726,7 @@ class AggregateTest(QueryTest):
 
 
 class ExistsTest(QueryTest, AssertsCompiledSQL):
+    __dialect__ = 'default'
 
     def test_exists(self):
         User = self.classes.User
@@ -1735,16 +1736,27 @@ class ExistsTest(QueryTest, AssertsCompiledSQL):
         self.assert_compile(sess.query(q1.exists()),
             'SELECT EXISTS ('
                 'SELECT 1 FROM users'
-            ') AS anon_1',
-            dialect=default.DefaultDialect()
+            ') AS anon_1'
         )
 
         q2 = sess.query(User).filter(User.name == 'fred')
         self.assert_compile(sess.query(q2.exists()),
             'SELECT EXISTS ('
                 'SELECT 1 FROM users WHERE users.name = :name_1'
-            ') AS anon_1',
-            dialect=default.DefaultDialect()
+            ') AS anon_1'
+        )
+
+    def test_exists_col_warning(self):
+        User = self.classes.User
+        Address = self.classes.Address
+        sess = create_session()
+
+        q1 = sess.query(User, Address).filter(User.id == Address.user_id)
+        self.assert_compile(sess.query(q1.exists()),
+            'SELECT EXISTS ('
+                'SELECT 1 FROM users, addresses '
+                'WHERE users.id = addresses.user_id'
+            ') AS anon_1'
         )