Opened 3 years ago
Closed 3 years ago
#33493 closed Cleanup/optimization (wontfix)
It's counter-intuitive how QuerySet.iterate() works with prefetch_related
| Reported by: | abetkin | Owned by: | nobody |
|---|---|---|---|
| Component: | Database layer (models, ORM) | Version: | dev |
| Severity: | Normal | Keywords: | |
| Cc: | Triage Stage: | Accepted | |
| Has patch: | no | Needs documentation: | no |
| Needs tests: | no | Patch needs improvement: | no |
| Easy pickings: | no | UI/UX: | no |
Description
Hi django fellows!
I've stumbled upon this code in the main branch: (see screenshot)
The usecase is iterating through a queryset with prefetch_related lookups specified.
Do I understand correctly that multiple database queries happen upon fetching every chunk, and also that multiple database connections are required?
If so, than I think it would be better just to prohibit the use of prefetch_related with QuerySet.iterate
Attachments (1)
Change History (4)
by , 3 years ago
| Attachment: | methods_that.png added |
|---|
comment:1 by , 3 years ago
| Component: | Uncategorized → Database layer (models, ORM) |
|---|---|
| Type: | Uncategorized → Bug |
comment:2 by , 3 years ago
| Triage Stage: | Unreviewed → Accepted |
|---|
comment:3 by , 3 years ago
| Resolution: | → wontfix |
|---|---|
| Status: | new → closed |
| Type: | Bug → Cleanup/optimization |
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Support for prefetching related objects with
QuerySet.iterator()was added in edbf930287cb72e9afab1f7208c24b1146b0c4ec, and yes an extra query is necessary for each chunk, it's documented. You can check related discussions in the ticket #29984, on the mailing list, and in PR. I don't see any reason to remove this feature.