Hi Tazo,
The default `output_field` of the `Avg` aggregate is a `FloatField`[1] hence
the error raised here. In the case of SQLite, `DurationField`s are stored as
large integers of microseconds[2] and the result returned by the database is
already a float making `float(value)` a no-op in `convert_value()`[3].
Since Django 1.9 it's possible to specify the `output_field` of an `Avg`
expression as documented[4].
In your case you want to do the following:
Questionnaire.objects.filter(
site_id=1
).annotate(
moyenne=Avg('chrono__temps', output_field=DurationField())
).values('title','moyenne')
Au plaisir,
Simon
[1]
https://github.com/django/django/blob/fdf5cd3429369954e8deb764d9f30f6374581613/django/db/models/aggregates.py#L45
[2] https://docs.djangoproject.com/en/1.9/ref/models/fields/#durationfield
[3]
https://github.com/django/django/blob/master/django/db/models/expressions.py#L282-L283
[4]
https://docs.djangoproject.com/en/1.9/ref/models/querysets/#django.db.models.Avg
Le samedi 2 avril 2016 13:08:20 UTC-4, Tazo Gil a écrit :
>
> Hello,
>
> The following request works in my dev django project (sqlite) by not in
> production with postgres
>
> out: >>>
> Questionnaire.objects.filter(site_id=1).annotate(moyenne=Avg('chrono__temps')).values('title','moyenne')
>
> The errors :
>
> out: Traceback (most recent call last):
> out: File "<console>", line 1, in <module>
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/query.py",
>
> line 234, in __repr__
> out: data = list(self[:REPR_OUTPUT_SIZE + 1])
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/query.py",
>
> line 258, in __iter__
> out: self._fetch_all()
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/query.py",
>
> line 1074, in _fetch_all
> out: self._result_cache = list(self.iterator())
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/query.py",
>
> line 112, in __iter__
> out: for row in compiler.results_iter():
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py",
>
> line 808, in results_iter
> out: row = self.apply_converters(row, converters)
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py",
>
> line 792, in apply_converters
> out: value = converter(value, expression, self.connection,
> self.query.context)
> out: File
> "/home/mimi/.virtualenvs/atmav2/local/lib/python2.7/site-packages/django/db/models/expressions.py",
>
> line 283, in convert_value
> out: return float(value)
> out: TypeError: float() argument must be a string or a number
>
> Thank you for your help.
>
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