Django on Windows (bug actually caused by Sqlite <=3.3.4 (3.3.5?))

(work in progress)

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Test suite failures

As of r8747 the test suite is showing the following failures when run on sqlite 3.2.7 and 3.3.4:

• On a test from tests/regressiontests/queries/models.py when using the sqlite3 Django DB backend.

tests/regressiontests/queries/models.py

This has been reported as ticket #7570.

This test fails:

Bug #7087 -- dates with extra select columns
>>> Item.objects.dates('created', 'day').extra(select={'a': 1})
[datetime.datetime(2007, 12, 19, 0, 0), datetime.datetime(2007, 12, 20, 0, 0)] 

Error is:

======================================================================
FAIL: Doctest: regressiontests.queries.models.__test__.API_TESTS
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\ramiro\django-trunk\django\test\_doctest.py", line 2180, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for regressiontests.queries.models.__test__.API_TESTS
  File "C:\ramiro\django-trunk\tests\regressiontests\queries\models.py", line unknown line number, in API_TESTS

----------------------------------------------------------------------
File "C:\ramiro\django-trunk\tests\regressiontests\queries\models.py", line ?, in regressiontests.queries.models.__test__.API_TESTS
Failed example:
    Item.objects.dates('created', 'day').extra(select={'a': 1})
Exception raised:
    Traceback (most recent call last):
      File "C:\ramiro\django-trunk\django\test\_doctest.py", line 1267, in __run
        compileflags, 1) in test.globs
      File "<doctest regressiontests.queries.models.__test__.API_TESTS[169]>", line 1, in <module>
        Item.objects.dates('created', 'day').extra(select={'a': 1})
      File "c:\ramiro\django-trunk\django\db\models\query.py", line 129, in __repr__
        return repr(list(self))
      File "c:\ramiro\django-trunk\django\db\models\query.py", line 141, in __len__
        self._result_cache.extend(list(self._iter))
      File "c:\ramiro\django-trunk\django\db\models\sql\subqueries.py", line 351, in results_iter
        for rows in self.execute_sql(MULTI):
      File "c:\ramiro\django-trunk\django\db\models\sql\query.py", line 1607, in execute_sql
        cursor.execute(sql, params)
      File "c:\ramiro\django-trunk\django\db\backends\sqlite3\base.py", line 136, in execute
        return Database.Cursor.execute(self, query, params)
    OperationalError: ORDER BY terms must not be non-integer constants


----------------------------------------------------------------------
Ran 253 tests in 433.032s

FAILED (failures=1)

A minimal models.py file that shows the problem (extracted from the above regression test):

"""
>>> time1 = datetime.datetime(2007, 12, 19, 22, 25, 0)
>>> time2 = datetime.datetime(2007, 12, 19, 21, 0, 0)
>>> time3 = datetime.datetime(2007, 12, 20, 22, 25, 0)
>>> time4 = datetime.datetime(2007, 12, 20, 21, 0, 0)
>>> i1 = Item(name='one', created=time1, modified=time1)
>>> i1.save()
>>> i2 = Item(name='two', created=time2)
>>> i2.save()
>>> i3 = Item(name='three', created=time3)
>>> i3.save()
>>> i4 = Item(name='four', created=time4)
>>> i4.save()

>>> Item.objects.dates('created', 'day').extra(select={'a': 1})
[datetime.datetime(2007, 12, 19, 0, 0), datetime.datetime(2007, 12, 20, 0, 0)]

"""

from django.db import models
import datetime

class Item(models.Model):
    name = models.CharField(max_length=10)
    created = models.DateTimeField()
    modified = models.DateTimeField(blank=True, null=True)

    class Meta:
        ordering = ['name']

    def __unicode__(self):
        return self.name

The SQL being generated by Django is correct:

>>> Item.objects.dates('created', 'day').extra(select={'a': 1}).query.as_sql()
('SELECT DISTINCT (1) AS "a", django_date_trunc("day", "sqlite3_dates_item"."created") FROM "sqlite3_dates_item" ORDER BY 1 ASC', ())

Problem seems to be related to some bug in the version of pysqlite2 or sqlite3 (main suspect) included with the official Python 2.5.2 win32 installer (2.3.2 and 3.3.4 respectively):

Python 2.5.2 (r252:60911, Feb 21 2008, 13:11:45) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from sqlite3 import dbapi2
>>> print dbapi2.version_info
(2, 3, 2)
>>> print dbapi2.sqlite_version_info
(3, 3, 4)

The win32 installer for Python 2.5 ships the same combination of pysqlite/sqlite versions and exhibits the same problem. The tests were also run under some other Windows- and Linux-based scenarios.

Summarizing:

Platform	Python version	pysqlite2 version	sqlite version	works?	Notes
win32	2.4.4	2.3.0 (external)	3.3.6	YES
Debian Linux	2.4.4	2.3.2 (external)	3.3.8	YES
win32	2.5	2.3.2 (built-in sqlite3)	3.3.4	NO
Debian Linux	2.5	2.3.2 (built-in sqlite3)	3.3.8	YES
win32	2.5.2	2.3.2 (built-in sqlite3)	3.3.4	NO
win32	2.5.2	2.4.1 (external)	3.5.2	YES	*
Debian Linux	2.5.2	2.3.2 (built-in sqlite3)	3.5.9	YES
custom Linux	2.5.2	?	3.2.7	NO

Note that the tests also fail under Linux with early sqlite versions.

Possible solution

As the table above shows, version <=3.3.4 of sqlite seems to be affected by this bug whilst version >=3.3.6 isn't (see ​http://sqlite.org/changes.html for possible hints).

As sqlite/pysqlite development continues, the pysqlite project keeps publishing new win32 binary installers for Python 2.5. Latest as of June 29, 2008 is version 2.4.1 (pysqlite-2.4.1.win32-py2.5.exe) that uses sqlite version 3.5.2 (see entry marked with * in the table above.)

How does this affect Django

The problem doesn't lie within Django itself, but leads to ask oneself if the order being used by the sqlite3 backed to try loading the sqlite DB-API2 modules (django/db/backends/sqlite3/base.py) shouldn't be inverted: Try loading pysqlite2 first and if this fails then try loading sqlite3:

base.

@@ -3 +3 @@
 
 Python 2.3 and 2.4 require pysqlite2 (http://pysqlite.org/).
 
-Python 2.5 and later use the sqlite3 module in the standard library.
+Python 2.5 and later use pysqlite2 or the sqlite3 module in the standard
+library.
 """
 
 from django.db.backends import BaseDatabaseWrapper, BaseDatabaseFeatures, BaseDatabaseOperations, util
 try:
     try:
-        from sqlite3 import dbapi2 as Database
-    except ImportError:
         from pysqlite2 import dbapi2 as Database
+    except ImportError:
+        from sqlite3 import dbapi2 as Database
 except ImportError, e:
     import sys
     from django.core.exceptions import ImproperlyConfigured

Reasoning behind this is that this would allow the user to take advantage of newer pysqlite2/sqlite3 versions he/she may have installed even if using Python 2.5.x. This might be true and desirable regardless of platform.

Deployment

• WindowsInstall
• wiki:django_apache_and_mod_wsgi
• ServerArrangements