Opened 10 years ago
Last modified 6 weeks ago
#25230 new Cleanup/optimization
Change to Query.get_count() causes big performance hit — at Version 1
| Reported by: | dexity | Owned by: | nobody |
|---|---|---|---|
| Component: | Database layer (models, ORM) | Version: | 1.8 |
| Severity: | Normal | Keywords: | |
| Cc: | Triage Stage: | Accepted | |
| Has patch: | yes | Needs documentation: | no |
| Needs tests: | no | Patch needs improvement: | yes |
| Easy pickings: | no | UI/UX: | no |
| Pull Requests: | |||
Description (last modified by ) ¶
Recent pull merge https://github.com/django/django/commit/c7fd9b242d2d63406f1de6cc3204e35aaa025233?diff=unified generates SQL which causes severe performance hit when using distinct parameter.
Instead of getting something like:
SELECT DISTINCT COUNT('*') FROM some_model;
it generates SQL query which looks:
SELECT COUNT('*') FROM (SELECT DISTINCT * FROM some_model) subquery;
Related ticket: https://code.djangoproject.com/ticket/23875
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