When using "select distinct" all ordering columns must be part of the output
(select) columns. We were previously just throwing away ordering columns that
weren't included, but there are some cases where they are needed and it's
difficult to add them in manually. So now the default behaviour is to append
any missing columns.
This can affect the output of distinct() if complicated order_by() constructs
are used, so the documentation has been updated with an explanation of what's
going on there.
Fixed#7070.
git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@7455 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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