#28683: Problems with the GIS Length annotation function
(django.contrib.gis.db.models.functions.Length)
--------------------------------------------+------------------------------
Reporter: Kordian Kowalski | Owner: nobody
Type: Bug | Status: new
Component: GIS | Version: 1.11
Severity: Normal | Keywords: gis geometry
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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In my use case, I am creating a Prefetch object that includes an
annotation with the GIS Length function as its base queryset.
The prefetch object is then being reused in multiple requests.
Only the first request succeeds, all subsequent requests fail with
following error messages:
`django.db.utils.ProgrammingError: function st_length(geography, boolean,
boolean) does not exist`
`django.db.utils.ProgrammingError: function st_length(geography, boolean,
boolean, boolean) does not exist`
`django.db.utils.ProgrammingError: function st_length(geography, boolean,
boolean, boolean, boolean) does not exist`
As you can see, there is an additional boolean value being passed in each
request.
I have narrowed down the issue to the following line
(django/contrib/gis/db/models/functions.py:347) :
{{{
def as_postgresql(self, compiler, connection):
(...)
self.source_expressions.append(Value(self.spheroid))
}}}
The additional boolean seems to be appended to params list every time the
prefetch object is compiled.
Also it seems that the problem may be affecting only postgres backends.
Steps to reproduce:
- create a model with a `django.contrib.gis.db.models.GeometryField`
- create a queryset with Length annotation: `qs =
MyModel.objects.annotate(my_length=Length('geometry'))`
- run `qs.all()` multiple times, all subsequent requests after the first
one will fail with the aforementioned message.
--
Ticket URL: <https://code.djangoproject.com/ticket/28683>
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