#25772: ArrayField: incorrent len lookup
----------------------------------+--------------------------------------
Reporter: mrAdm | Owner:
Type: Bug | Status: new
Component: contrib.postgres | Version: 1.8
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
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Changes (by mrAdm):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> Models:
> {{{
> NullableIntegerArrayModel.objects.create(field=[])
> NullableIntegerArrayModel.objects.create(field=[1])
> NullableIntegerArrayModel.objects.create(field=[2, 3])
> NullableIntegerArrayModel.objects.create(field=[20, 30, 40])
> NullableIntegerArrayModel.objects.create(field=None)
> }}}
>
> Queries:
> {{{
> NullableIntegerArrayModel.objects.filter(field__len=0)
> # return: empty queryset
> NullableIntegerArrayModel.objects.filter(field__len__lt=2)
> # return only one model (field=[1])
> }}}
>
> Reason:
> PostgreSQL function array_length(ARRAY[]::int4[], 1) return null if array
> empty.
>
> The solution is to use a function PostgreSQL: COALESCE ().
> {{{
> SELECT * FROM ... WHERE COALESCE(array_length("field", 1), 0)=0
> }}}
New description:
Models:
{{{
NullableIntegerArrayModel.objects.create(field=[])
NullableIntegerArrayModel.objects.create(field=[1])
NullableIntegerArrayModel.objects.create(field=[2, 3])
NullableIntegerArrayModel.objects.create(field=[20, 30, 40])
}}}
Queries:
{{{
NullableIntegerArrayModel.objects.filter(field__len=0)
# return: empty queryset
NullableIntegerArrayModel.objects.filter(field__len__lt=2)
# return only one model (field=[1])
}}}
Reason:
PostgreSQL function array_length(ARRAY[]::int4[], 1) return null if array
empty.
The solution is to use a function PostgreSQL: COALESCE ().
{{{
SELECT * FROM ... WHERE COALESCE(array_length("field", 1), 0)=0
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/25772#comment:1>
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