#30124: QuerySet.only() on reverse many-to-one relationship causes extra
database
queries
-------------------------------------+-------------------------------------
Reporter: Beda Kosata | Owner: Dan Davis
Type: Bug | Status: assigned
Component: Database layer | Version: 2.1
(models, ORM) |
Severity: Normal | 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):
Having spent a bit of time in refactoring `only` and `defer` for #21204
([https://github.com/django/django/pull/15985 PR]) I think the proper
solution is likely not to introspect aliases and try to make the best of
it but to add a new attribute to `Query` that denotes fields that must
always be present when the select mask is generated.
We already do so for all primary keys of models involved in
`select_related`/`only` or `defer` combinations so if this attribute was
present and the `get_queryset` method of reverse manager set it as
`queryset.query.select_mask = {rel}` and then a copy of this value could
be used in ` _get_defer_select_mask` and ` _get_only_select_mask`.
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Ticket URL: <https://code.djangoproject.com/ticket/30124#comment:6>
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