#11387: order_by over a GenericRelation generates incorrect SQL
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Reporter: adurdin | Owner: mtredinnick
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: SVN
Resolution: | Keywords:
Stage: Design decision needed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 1
Needs_better_patch: 0 |
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Changes (by adurdin):
* needs_better_patch: => 0
* stage: Unreviewed => Design decision needed
* needs_tests: => 1
* needs_docs: => 0
Comment:
I’ve been thinking about the problem some more, and that test is wrong,
and here’s why:
If you order_by across a reverse ForeignKey relation, a LEFT JOIN is
created to the target table. So if you order_by across a reverse
GenericForeignKey relation, it should also create a LEFT JOIN to the
target table.
There is a deeper problem here, I believe. The correct query for this
case should be:
{{{
SELECT "foo_foo"."id" FROM "foo_foo" LEFT OUTER JOIN "foo_bar" ON
("foo_foo"."id" = "foo_bar"."object_id" AND "foo_bar"."content_type_id" =
%s) ORDER BY "foo_bar"."id" ASC', (8,))
}}}
But as far as I have been able to determine, the query generation does not
support multiple join conditions, and I don't believe it is possible to
transform the above query to move the second condition to the WHERE
clause. This means that the query generation code will have to be amended
in numerous places to support multiple join conditions. I fear patching
this is beyond me.
--
Ticket URL: <http://code.djangoproject.com/ticket/11387#comment:1>
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