id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
27862	Exists() feature generates invalid SQL query on postgres backend	Vasily Stepanov	Matthew Schinckel	"Exists() feature, implemented in #27149 ticket, not working properly on postgres backend.
This happens only in complex queries, where django has to use table aliases.
Consider the following models:
{{{
class Foo(models.Model):
    spam1 = models.ForeignKey('Spam', on_delete=models.CASCADE, related_name='+')
    spam2 = models.ForeignKey('Spam', on_delete=models.CASCADE, related_name='+')


class Bar(models.Model):
    name1 = models.CharField(max_length=200)
    name2 = models.CharField(max_length=200)


class Spam(models.Model):
    name = models.CharField(max_length=200)
}}}

And the code:
{{{
bars = models.Bar.objects.filter(
        name1=OuterRef('spam1__name'),
        name2=OuterRef('spam2__name'))

qs = models.Foo.objects.annotate(bars=Exists(bars))
qs = qs.filter(bars=True)
}}}
This SQL generated using {{{django.db.backends.postgresql}}} backend:
{{{
SELECT
    ""demo_foo"".""id"", ""demo_foo"".""spam1_id"",
    ""demo_foo"".""spam2_id"",
    EXISTS(
        SELECT U0.""id"", U0.""name1"", U0.""name2""
          FROM ""demo_bar"" U0
         WHERE (U0.""name2"" = (""demo_spam"".""name"") AND U0.""name1"" = (""T3"".""name""))) AS ""bars""
  FROM ""demo_foo""
INNER JOIN ""demo_spam"" ON (""demo_foo"".""spam2_id"" = ""demo_spam"".""id"")
INNER JOIN ""demo_spam"" T3 ON (""demo_foo"".""spam1_id"" = T3.""id"")
WHERE EXISTS(
    SELECT U0.""id"", U0.""name1"", U0.""name2""
      FROM ""demo_bar"" U0
     WHERE (U0.""name2"" = (""demo_spam"".""name"") AND U0.""name1"" = (""T3"".""name""))) = True
}}}
which ends up with this error:
{{{
django.db.utils.ProgrammingError: missing FROM-clause entry for table ""T3""
LINE 1: ....""name1"" = (""demo_spam"".""name"") AND U0.""name2"" = (""T3"".""name...
                                                             ^
}}}

This happens because of quotes around {{{T3}}}.

SQL works as expected, if you remove these quotes and execute it manually."	Bug	closed	Database layer (models, ORM)	1.11	Release blocker	fixed	Queryset Subquery Exists	Matthew Schinckel	Ready for checkin	1	0	0	0	0	0