[Sqlalchemy-tickets] [sqlalchemy] #2818: Query.exists() don't works with queries without filters

[sqlalchemy <mi...@zz...>]

#2818: Query.exists() don't works with queries without filters
------------------------+-----------------------------------------
 Reporter:  vmagamedov  |           Owner:  zzzeek
     Type:  defect      |          Status:  new
 Priority:  medium      |       Milestone:  0.8.xx
Component:  orm         |        Severity:  no triage selected yet
 Keywords:              |  Progress State:  awaiting triage
------------------------+-----------------------------------------
 Action:
 {{{
 #!python
 db.session.query(User).exists()
 }}}
 Expectation:
 {{{
 #!sql
 SELECT 1 FROM users
 }}}
 Current result:
 {{{
 #!sql
 SELECT 1
 }}}
 Solution:
 {{{
 #!diff
 diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
 index b71bfe0..d64575a 100644
 --- a/lib/sqlalchemy/orm/query.py
 +++ b/lib/sqlalchemy/orm/query.py
 @@ -2494,7 +2494,7 @@ class Query(object):
          .. versionadded:: 0.8.1

          """
 -        return sql.exists(self.with_entities('1').statement)
 +        return sql.exists(self.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 0973dc3..bc56668 100644
 --- a/test/orm/test_query.py
 +++ b/test/orm/test_query.py
 @@ -1730,9 +1730,16 @@ class ExistsTest(QueryTest, AssertsCompiledSQL):
      def test_exists(self):
          User = self.classes.User
          sess = create_session()
 -        q1 = sess.query(User).filter(User.name == 'fred')
 +        q1 = sess.query(User)
          self.assert_compile(sess.query(q1.exists()),
              'SELECT EXISTS ('
 +                'SELECT 1 FROM users'
 +            ') AS anon_1',
 +            dialect=default.DefaultDialect()
 +        )
 +        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()
 }}}
 P.S. Is it normal to send pull requests on !GitHub? Or you prefer
 Trac/patches?

--
Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2818>
sqlalchemy <http://www.sqlalchemy.org/>
The Database Toolkit for Python