test0908
/
django
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

[1.7.x] Documented a current limitation of multiple table annotation; refs #10060. 

Backport of 4b23a6c7a9 from master
This commit is contained in:
Benjamin Bach 2014-12-01 00:02:43 +01:00 committed by Tim Graham
parent 82c0c7b34f
commit 48bd44670b
1 changed files with 11 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
docs/topics/db/aggregation.txt
View File

@ -179,6 +179,17 @@ of the ``annotate()`` clause is a ``QuerySet``; this ``QuerySet`` can be
modified using any other ``QuerySet`` operation, including ``filter()``, modified using any other ``QuerySet`` operation, including ``filter()``,
``order_by()``, or even additional calls to ``annotate()``. ``order_by()``, or even additional calls to ``annotate()``.
.. admonition:: If in doubt, inspect the SQL query!
In order to understand what happens in your query, consider inspecting the
``query`` property of your ``QuerySet``.
For instance, combining multiple aggregations with ``annotate()`` will
yield the wrong results, as `multiple tables are the cross joined`_,
resulting in duplicate row aggregations.
.. _multiple tables are the cross joined: https://code.djangoproject.com/ticket/10060
Joins and aggregates Joins and aggregates
==================== ====================