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| author | Tim Graham <timograham@gmail.com> | 2015-12-08 16:45:15 -0500 |
|---|---|---|
| committer | Tim Graham <timograham@gmail.com> | 2015-12-15 07:59:37 -0500 |
| commit | 3d2236773ba88e330841b8c72183b0e978e10909 (patch) | |
| tree | 5d82f45d55eb5e76c1cccde545d6312b908a1ed6 | |
| parent | 69b69f6d6085d80ccf36a3e999e9e5b98d580786 (diff) | |
Refs #10060 -- Corrected description of multiple annotations bug.
| -rw-r--r-- | docs/topics/db/aggregation.txt | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/docs/topics/db/aggregation.txt b/docs/topics/db/aggregation.txt index 030335c908..4838663beb 100644 --- a/docs/topics/db/aggregation.txt +++ b/docs/topics/db/aggregation.txt @@ -190,9 +190,8 @@ Combining multiple aggregations ------------------------------- Combining multiple aggregations with ``annotate()`` will `yield the wrong -results <https://code.djangoproject.com/ticket/10060>`_, as multiple tables are -cross joined. Due to the use of ``LEFT OUTER JOIN``, duplicate records will be -generated if some of the joined tables contain more records than the others: +results <https://code.djangoproject.com/ticket/10060>`_ because joins are used +instead of subqueries: >>> Book.objects.first().authors.count() 2 @@ -374,8 +373,8 @@ Both queries return a list of publishers that have at least one book with a rating exceeding 3.0, hence publisher C is excluded. In the first query, the annotation precedes the filter, so the filter has no -effect on the annotation. ``distinct=True`` is required to avoid a -:ref:`cross-join bug <combining-multiple-aggregations>`. +effect on the annotation. ``distinct=True`` is required to avoid a :ref:`query +bug <combining-multiple-aggregations>`. The second query counts the number of books that have a rating exceeding 3.0 for each publisher. The filter precedes the annotation, so the filter |