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Fixed #10929 -- Added default argument to aggregates.

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Thanks to Simon Charette and Adam Johnson for the reviews.
This commit is contained in:
Nick Pope 2021-02-21 01:38:55 +00:00 • committed by Mariusz Felisiak
parent 59942a66ce
commit 501a8db465
11 changed files with 393 additions and 64 deletions
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15
docs/ref/models/database-functions.txt
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@ -59,7 +59,7 @@ will result in a database error.
Usage examples::
>>> # Get a screen name from least to most public
>>> from django.db.models import Sum, Value as V
>>> from django.db.models import Sum
>>> from django.db.models.functions import Coalesce
>>> Author.objects.create(name='Margaret Smith', goes_by='Maggie')
>>> author = Author.objects.annotate(
@ -68,13 +68,18 @@ Usage examples::
Maggie
>>> # Prevent an aggregate Sum() from returning None
>>> # The aggregate default argument uses Coalesce() under the hood.
>>> aggregated = Author.objects.aggregate(
... combined_age=Coalesce(Sum('age'), V(0)),
... combined_age_default=Sum('age'))
... combined_age=Sum('age'),
... combined_age_default=Sum('age', default=0),
... combined_age_coalesce=Coalesce(Sum('age'), 0),
... )
>>> print(aggregated['combined_age'])
0
>>> print(aggregated['combined_age_default'])
None
>>> print(aggregated['combined_age_default'])
0
>>> print(aggregated['combined_age_coalesce'])
0
.. warning::