#25230: Change to Query.get_count() causes big performance hit
-------------------------------------+-------------------------------------
Reporter: dexity | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: 1.8
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by dexity):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> https://code.djangoproject.com/ticket/23875
> 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;}}}
New description:
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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Ticket URL: <https://code.djangoproject.com/ticket/25230#comment:1>
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