#34413 closed New feature (duplicate)
Variant of Prefetch but for the earliest/latest related object — at Version 4
Reported by: | Willem Van Onsem | Owned by: | nobody |
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Component: | Database layer (models, ORM) | Version: | dev |
Severity: | Normal | Keywords: | |
Cc: | Triage Stage: | Unreviewed | |
Has patch: | yes | Needs documentation: | no |
Needs tests: | yes | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description (last modified by )
What would happen if we span over multiple relations, like:
User.objects.prefetch_related( Prefetch("groups__permissions", queryset=Permission.objects.order_by('codename')[:1], to_attr="first_permission") )
Change History (5)
by , 21 months ago
Attachment: | prefetching_the_earliest_latest_related_object_.patch added |
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comment:1 by , 21 months ago
Needs tests: | set |
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comment:2 by , 21 months ago
Description: | modified (diff) |
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comment:3 by , 21 months ago
Resolution: | → duplicate |
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Status: | assigned → closed |
comment:4 by , 21 months ago
Description: | modified (diff) |
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Pretty sure this is a duplicate of #26780 fixed in the soon to be released 4.2.
Since 242499f2dc2bf24a9a5c855690a2e13d3303581a
Prefetch(queryset)
supports slicing through the use of filtering over partitioned rank (RANK() OVER (PARTITION BY <join_field> ORDER BY <order_by>
) so earliest and latest related objects (or any slice of related objects for that matter) can be prefetched.