Django 1.5.1: severe performance degradation on Oracle

[zakharov.vv@…]

After migrating to Django 1.5.1, several queries takes thousands times more time comparing to Django 1.4.5.

Example query generated by ORM:

SELECT COUNT(*) FROM "TICKETS" WHERE ("TICKETS"."T_TYPE" IN (:arg0, :arg1, :arg2, :arg3) AND "TICKETS"."T_PARTNER_CODE" = :arg4 AND "TICKETS"."T_CHANEL" = :arg5 AND "TICKETS"."T_WORKER_CODE" = :arg6 AND "TICKETS"."T_CDATE" <= :arg7 AND "TICKETS"."T_CDATE" >= :arg8 )

Django 1.4.5: ~7ms
Django 1.5.1: ~193574ms (about 27000 times more!)

git bisect points to this commit: ​https://github.com/django/django/commit/d194f290571f7e9dda7d2fd7a6f2b171120f2f14. Indeed, forcing convert_unicode to be equal to force_bytes solves the issue.

The only found difference is in params to query:
Django 1.4.5:

[1, 38, 76, 92, '777-61', 61, 'pupkin', '2013-07-03 00:00:00', '2013-06-01 00:00:00']

Django 1.5.1:

[1, 38, 76, 92, u'777-61', 61, u'pupkin', u'2013-07-03 00:00:00', u'2013-06-01 00:00:00']

Django 1.5.1 hangs on this string (django/db/backends/oracle/base.py:710):

            return self.cursor.execute(query, self._param_generator(params))

Directly using cx_Oracle for this query shows no difference for two variants of query params.

Used versions:

• cx-Oracle 5.1.2
• instantclient 11.2.0.3.0 (same for instantclient 10.2.0.5)
• Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

[zakharov.vv@…]

It seems, that issue affects only large tables. Table from example in description has about 100 million records. For small tables (thousands records) query time doesn't change after upgrading to 1.5.1.

[wim@…]

Accepted. If you would like to contribute and would like to submit a patch (or even a pull request), you are welcome to do so!

[Shai Berger]

Hi,

This ticket refers to versions of Django (1.5) and Oracle server (10g) which are no longer supported by their respective vendors, so I am closing it.

If the problem can be reproduced on newer versions (Oracle>=11 and Django>=1.7), please re-open.

(Although Django 1.7 nominally supports Oracle 10g, the core team has no access to an Oracle 10 server, which makes it very hard for us to solve problems against it).