#31150: Subquery annotations are omitted in group by query section if multiple
annotation are declared
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Reporter: Johannes Hoppe | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 3.0
(models, ORM) |
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
Thanks for the extra details, I think I have a better picture of what's
happening here.
In the cases where an outer query spawns a multi-valued relationship and
the subquery references one of these multi-valued relationship we must
keep grouping by the subquery.
In your original reports the `INNER JOIN "camps_bookingoption" T4` joins
spawns multiple rows for the same `camps.Offer` and then your subquery
filter against `(T4."position")` which
In ORM terms that means we must keep returning `self` in
`Subquery.get_group_by_cols` when any of our `OuterRef` include a `__`
which could point to a multi-valued relationship.
We could go a bit further and only disable the optimization if any of the
outer-ref in the `__` chain is multi-valued by relying on `getattr(rel,
'many_to_many', True)` introspection but in all cases that means adding a
way to ''taint'' `Col` instances with whether or not they are/could be
multi-valued so `get_group_by_cols` can `return self` if any of
`get_external_cols` is multi-valued
I could see this tainting as being useful to warn about #10060 in the
future since the logic could be based on this column or alias tainting.
I'm happy to submit a patch or discuss any alternatives but it feels like
the above solution solves the reported problem while maintaining the
optimization for most of the cases.
--
Ticket URL: <https://code.djangoproject.com/ticket/31150#comment:10>
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