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Fixed #25534, Fixed #31639 -- Added support for transform references in expressions.

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Thanks Mariusz Felisiak and Simon Charette for reviews.
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Ian Foote 2020-11-15 22:43:47 +00:00 • committed by Mariusz Felisiak
parent e46ca51c24
commit 8b040e3cbb
14 changed files with 354 additions and 82 deletions
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30
docs/topics/db/queries.txt
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@ -669,6 +669,36 @@ The ``F()`` objects support bitwise operations by ``.bitand()``, ``.bitor()``,
Support for ``.bitxor()`` was added.
.. _using-transforms-in-expressions:
Expressions can reference transforms
------------------------------------
.. versionadded: 3.2
Django supports using transforms in expressions.
For example, to find all ``Entry`` objects published in the same year as they
were last modified::
>>> Entry.objects.filter(pub_date__year=F('mod_date__year'))
To find the earliest year an entry was published, we can issue the query::
>>> Entry.objects.aggregate(first_published_year=Min('pub_date__year'))
This example finds the value of the highest rated entry and the total number
of comments on all entries for each year::
>>> Entry.objects.values('pub_date__year').annotate(
... top_rating=Subquery(
... Entry.objects.filter(
... pub_date__year=OuterRef('pub_date__year'),
... ).order_by('-rating').values('rating')[:1]
... ),
... total_comments=Sum('number_of_comments'),
... )
The ``pk`` lookup shortcut
--------------------------