#6422: Support for 'DISTINCT ON' queries with QuerySet.distinct()
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Reporter: Manfred Wassmann | Owner: jgelens
<manolo@…> | Status: assigned
Type: New feature | Version: SVN
Component: Database layer | Resolution:
(models, ORM) | Triage Stage: Accepted
Severity: Normal | Needs documentation: 0
Keywords: dceu2011 | Patch needs improvement: 0
Has patch: 1 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by akaariai):
Some comments (I haven't actually tried the patch, just read it in
diffview):
- IMHO add_distinct_fields needs a docstring. Other similar methods seem
to have one, also.
- What happens if you specify .distinct(field_list) multiple times with
different fields? If the first .distinct call generated joins, won't those
joins be left loitering around without any users, but still having
refcount > 0?
- Haven't tested this, but I suspect you can break this by adding fields
to DISTINCT ON which aren't in the normal select list and then doing a
group by. If you want correct results in this case, you will probably need
to subquerify the DISTINCT ON query, then do a group by.
NotImplementedError seems to be the sane choice, making this work
correctly might be a bit hard and I haven't ever used distinct on + group
by combination when writing SQL myself.
The true_or_false argument was removed. Is there any way to get rid of the
distinct after this. Does there need to be one?
--
Ticket URL: <https://code.djangoproject.com/ticket/6422#comment:57>
Django <https://code.djangoproject.com/>
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