#26434: Inconsistent results of QuerySet.count() when ordering is not a subset
of
explicit grouping.
-------------------------------------+-------------------------------------
Reporter: kamandol | Owner: Michal
| Mládek
Type: Bug | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: postgresql queryset | Triage Stage: Accepted
count annotate aggreagate |
order_by |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Simon Charette):
> Using order_by('...') on a column that is also used implicitly for
grouping in an aggregation queryset is a misuse of the ORM AFAIK. So what
should we do about it?
I share your sentiment that a warning should be emitted but that likely
warrant a separate ticket inspired by #14357, #32546 (there might be one
already I just can't find it now).
I think we should keep this one focused on making sure the right results
are returned in the mean time as it's caused by an over-eager optimization
(pruning an `ORDER BY` for performance reasons).
The way things are currently setup the ''not quite correct'' example is
wrong as the `order_by("name")` is elided when `count()` is called but not
when the full query is materialized.
The example you linked is about aggregate function annotations but
[https://dryorm.xterm.info/ticket-26434 you'll notice that the gotcha is
not honored when aggregation is used].
--
Ticket URL: <https://code.djangoproject.com/ticket/26434#comment:18>
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