#19263: DatabaseError on using empty Page .object_list in __in clause in a query
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Reporter: chkwok@… | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 1.4
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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I've noticed that after upgrading to Django 1.4, __in queries really don't
like empty sets. Simple queries still work, like
User.objects.filter(groups__in=[]), but most failures I've seen are with
Paginators. I think this is the minimum set to cause a DatabaseError,
create any app, add a models.py with:
{{{#!python
from django.db import models
class Author(models.Model):
pass
class Book(models.Model):
author = models.ForeignKey(Author)
def crash():
from django.core.paginator import Paginator
pages = Paginator(Author.objects.all(), 25)
page = pages.page(1)
books = Book.objects.filter(author__in=page.object_list)
print books
}}}
calling crash() will cause this stack trace:
{{{
C:\Workspace\someproject\src\someproject\test.py in <module>()
6
7 books = Book.objects.filter(author__in=page.object_list)
----> 8 print books
9
C:\Dev\Python27\lib\site-packages\django\db\models\query.pyc in
__repr__(self)
70
71 def __repr__(self):
---> 72 data = list(self[:REPR_OUTPUT_SIZE + 1])
73 if len(data) > REPR_OUTPUT_SIZE:
74 data[-1] = "...(remaining elements truncated)..."
C:\Dev\Python27\lib\site-packages\django\db\models\query.pyc in
__len__(self)
85 self._result_cache = list(self.iterator())
86 elif self._iter:
---> 87 self._result_cache.extend(self._iter)
88 if self._prefetch_related_lookups and not
self._prefetch_done:
89 self._prefetch_related_objects()
C:\Dev\Python27\lib\site-packages\django\db\models\query.pyc in
iterator(self)
289 klass_info = get_klass_info(model,
max_depth=max_depth,
290 requested=requested,
only_load=only_load)
--> 291 for row in compiler.results_iter():
292 if fill_cache:
293 obj, _ = get_cached_row(row, index_start, db,
klass_info,
C:\Dev\Python27\lib\site-packages\django\db\models\sql\compiler.pyc in
results_iter(self)
761 if self.query.select_for_update and
transaction.is_managed(self.using):
762 transaction.set_dirty(self.using)
--> 763 for rows in self.execute_sql(MULTI):
764 for row in rows:
765 if resolve_columns:
C:\Dev\Python27\lib\site-packages\django\db\models\sql\compiler.pyc in
execute_sql(self, result_type)
816
817 cursor = self.connection.cursor()
--> 818 cursor.execute(sql, params)
819
820 if not result_type:
C:\Dev\Python27\lib\site-packages\django\db\backends\util.pyc in
execute(self, sql, params)
38 start = time()
39 try:
---> 40 return self.cursor.execute(sql, params)
41 finally:
42 stop = time()
C:\Dev\Python27\lib\site-
packages\django\db\backends\postgresql_psycopg2\base.pyc in execute(self,
query, args)
50 def execute(self, query, args=None):
51 try:
---> 52 return self.cursor.execute(query, args)
53 except Database.IntegrityError, e:
54 raise utils.IntegrityError,
utils.IntegrityError(*tuple(e)), sys.exc_info()[2]
DatabaseError: syntax error at or near ")"
LINE 1: ...ugtest_book" WHERE "bugtest_book"."author_id" IN () LIMIT 21
}}}
The SQL statement created is:
{{{
SELECT "bugtest_book"."id", "bugtest_book"."author_id" FROM "bugtest_book"
WHERE "bugtest_book"."author_id" IN () LIMIT 21
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/19263>
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