#32685: Add feature to preserve order in .filter(field__in=list) query
-------------------------------------+-------------------------------------
Reporter: Barney Szabolcs | Owner: nobody
Type: New feature | Status: closed
Component: Database layer | Version: 2.2
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Barney Szabolcs:
Old description:
> filter {{{__in}}} query does not guarantee to preserve order, so I
> usually sort afterwards using python's sort.
>
> However, in **django admin** I cannot sort queries using python's sort
> when manipulating the QuerySet
> since I have to return a QuerySet.
> So, I'd do something like
> {{{
> queryset.filter(my_field__in=my_values).raw(
> f'order by array_position(ARRAY[{ ",".join(["%s"]*len(my_values))
> }]::varchar[], my_field)',
> params=my_values)
> }}}
> but this does not work...
> is there a solution here? (I cannot use raw either since I have a
> queryset input argument to work with)
>
> **UPDATE:**
>
> now, I've found a cryptic solution:
> https://stackoverflow.com/a/37648265/1031191
>
> {{{
> from django.db.models import Case, When
>
> preserved = Case(*[When(my_field=val, then=pos) for pos, val in
> enumerate(my_values)])
> queryset.filter(my_field__in=my_values).order_by(preserved)
> }}}
> I think Django should provide a better way than this.
>
> Maybe {{{ queryset.filter(my_field__in_preserve=my_values) }}}
New description:
filter {{{__in}}} query does not guarantee to preserve order, so I usually
sort afterwards using python's sort.
However, in **django admin** I cannot sort queries using python's sort
when manipulating the QuerySet
since I have to return a QuerySet.
So, I'd do something like
{{{
queryset.filter(my_field__in=my_values).raw(
f'order by array_position(ARRAY[{ ",".join(["%s"]*len(my_values))
}]::varchar[], my_field)',
params=my_values)
}}}
but this does not work...
is there a solution here? (I cannot use raw either since I have a
queryset input argument to work with)
**UPDATE:**
now, I've found a cryptic solution:
https://stackoverflow.com/a/37648265/1031191
{{{
from django.db.models import Case, When
preserved = Case(*[When(my_field=val, then=pos) for pos, val in
enumerate(my_values)], default=len(my_values))
queryset.filter(my_field__in=my_values).order_by(preserved)
}}}
I think Django should provide a better way than this.
Maybe {{{ queryset.filter(my_field__in_preserve=my_values) }}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/32685#comment:3>
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