#17974: .distint('FIELDNAME') FAILS for MySQL
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Reporter: mschettler@… | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 1.4
(models, ORM) | Resolution: invalid
Severity: Normal | Triage Stage:
Keywords: distinct on | Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by akaariai):
If you can make .distinct('somefield') work on MySQL it would be very
welcome addition. I believe it is somewhat hard to write that patch
correctly (particularly, how to make .order_by() + .distinct() work
correctly). MySQL doesn't have DISTINCT ON (fields), so you need something
like this: http://stackoverflow.com/questions/5804529/distinct-on-
multiple-columns.
Of course, if you want just distinct somefield values, instead of the full
DISTINCT ON semantics, then qs.values_list('somefield').distinct() should
work.
Why is there DISTINCT ON implementation that works only on PostgreSQL? The
choice was to not support this at all, or support this only on PostgreSQL.
The distinct(*fields) is very useful in certain cases, so I think having
it on PostgreSQL only is better than not having it at all.
--
Ticket URL: <https://code.djangoproject.com/ticket/17974#comment:9>
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