#30349: Using exclude on annotated FilteredRelation doesn't work
-------------------------------------+-------------------------------------
Reporter: Lucas Miller | Owner: robinh00d
Type: Bug | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* stage: Ready for checkin => Accepted
Comment:
> So the result returned is not the result we are expecting, and the query
should look like :
Could you submit an additional test that demonstrate the wrong results are
returned.
The query you are suggesting seems problematic because the
`book_alice."id" IS NULL` predicate contradicts the use of an `INNER JOIN`
which should already filters out null results. In other words this query
cannot match any row because the `INNER JOIN` will only return results in
both sets and thus `book_alice."id" IS NOT NULL` will always be true.
This kind of match can only be generated using a `LEFT OUTER JOIN` which
some form of row grouping or a subquery pushdown which is what the ORM
prefers to do.
I think the appropriate query should be
{{{#!sql
SELECT
"filtered_relation_author"."id",
"filtered_relation_author"."name",
"filtered_relation_author"."content_type_id",
"filtered_relation_author"."object_id"
FROM
"filtered_relation_author"
WHERE NOT (
"filtered_relation_author"."id" IN (
SELECT
U1."author_id"
FROM
"filtered_relation_book"
WHERE
"filtered_relation_book"."title" LIKE 'poem by alice'
)
)
}}}
I guess `split_exclude` need to be adjusted to special case `filter_expr`
that refer to a filtered expression instead of simply copy'ing
`filtered_expressions` around.
--
Ticket URL: <https://code.djangoproject.com/ticket/30349#comment:6>
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