Opened 8 weeks ago
Last modified 7 weeks ago
#36507 assigned Cleanup/optimization
Document that only the base queryset’s prefetch_related() is preserved when using union() — at Version 1
| Reported by: | Clifford Gama | Owned by: | |
|---|---|---|---|
| Component: | Database layer (models, ORM) | Version: | 5.2 |
| Severity: | Normal | Keywords: | prefetch_related, union |
| Cc: | Sniom | Triage Stage: | Accepted |
| Has patch: | no | Needs documentation: | no |
| Needs tests: | no | Patch needs improvement: | no |
| Easy pickings: | no | UI/UX: | no |
Description (last modified by )
When using QuerySet.union() (possibly also intersection() and difference()) in Django, any prefetch_related() applied to the second (and third, etc) queryset is silently ignored. See forum thread in which it was suggested to open a documentation ticket. A docs improvement should also likely include the workaround for using Q objects to do all prefetches in the base qs (where possible), which is suggested by Simon in the forum.
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