#15819: Admin searches should use distinct, if query involves joins
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Reporter: Adam Kochanowski | Owner: ryankask
<aip@…> | Status: reopened
Type: Bug | Version: SVN
Component: contrib.admin | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: | Needs documentation: 0
Has patch: 1 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Comment (by akaariai):
Maybe the queryset should expose some way to tell if distinct should be
used? The queryset should contain that logic, the admin should not try to
duplicate / guess that. It would be pretty easy to set a flag
"contains_multijoin" whenever such a join is seen in
sql/query/setup_joins, and after that Admin could just do if
qs.query.contains_multijoin: qs = qs.distinct().
It would be possible to generate queries in a way that distinct isn't
needed at all. This can be done using subqueries instead of joins for
reverse fk/m2m filters. Unfortunately some backends will likely choke on
such queries (while others will benefit) so just changing the ORM to use
subqueries isn't possible, or at least the backwards compatibility issues
should be investigated thoroughly. In addition, changing the ORM code to
generate such queries isn't the easiest thing to do, so that is another
problem for this path.
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Ticket URL: <https://code.djangoproject.com/ticket/15819#comment:17>
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