#18375: F() doesn't work as expected across multijoin relations
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Reporter: FunkyBob | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.4
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: | Needs documentation: 0
Has patch: 0 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Changes (by akaariai):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
* type: Uncategorized => Bug
* stage: Unreviewed => Accepted
Comment:
To me this seems like a bug, or at least non-wanted behavior. Usually
references inside one operation target the same alias, for example
`filter(unter__available__gt=1, unter__exact=foo)` should target the same
unter reference, while
`filter(unter__available__gt=1).filter(unter__exact=foo)` should target
different references.
If this can be fixed at this point needs at least some consideration. The
change could break existing queries, and there wouldn't be any way to get
the original behavior back, as you can split one filter clause to two
different filter operations.
I have been thinking that it would be useful to be able to annotate the
relations in the query. So, you could do:
{{{
.annotate(unter_ref='unter').filter(unter_ref__available__gt=F('unter_ref__used'))
OR
.annotate(unter_ref1='unter',
unter_ref2='unter').filter(unter_ref1__available__gt=F('unter_ref2__used'))
}}}
The first would generate the query you are looking for, the second would
generate what you get now. However there is a long way to get to the point
where you can use the annotate() like in the example.
I am marking this as accepted. The reasoning is that the reference under
the same .filter() call should target the same relation, and that the
current behavior doesn't seem that useful. Backwards compatibility could
turn this decision however.
For the time being I can't figure out a way to generate the query you want
without using qs.extra().
--
Ticket URL: <https://code.djangoproject.com/ticket/18375#comment:1>
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