#35810: Provide `Select` class for `select_related` (like `Prefetch` exists for
`prefetch_related`)
-------------------------------------+-------------------------------------
Reporter: Bart van Andel | Owner: (none)
Type: New feature | Status: new
Component: Database layer | Version: 5.1
(models, ORM) |
Severity: Normal | Resolution:
Keywords: query optimization | Triage Stage:
| Unreviewed
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 Bart van Andel):
Note: I tried to optimize our use case like this (pseudo code):
{{{
if self.message_set.is_loaded:
return max(self.message_set.all(), key=lambda item: item.created_at,
default=None)
# or, more clearly, but also not possible:
return self.message_set.latest("created_at", trust_cached_data=True)
else:
return self.message_set.latest("created_at")
# or, even more clearly, just get the value directly, using preloaded data
if it exists:
return self.message_set.latest("created_at", trust_cached_data=True)
}}}
There is no `is_loaded` or `trust_cached_data` (or equivalents) however,
so this obviously won't work. Also, obviously this should be used with
extreme care, but then again, when optimizing you sometimes need to be
careful and creative anyway.
--
Ticket URL: <https://code.djangoproject.com/ticket/35810#comment:1>
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