From: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
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To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Optimize query for listing un-read messages |
Date: | 2014-05-01 22:55:25 |
Message-ID: | 1398984925338-5802170.post@n5.nabble.com |
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Lists: | pgsql-performance |
Andreas Joseph Krogh-2 wrote
> I will end up with that only if
> all users read all messages, which is not nearly the case.
These observations probably won't help but...
You have what amounts to a mathematical "spare matrix" problem on your
hands...
Is there any way to expire messages so that dimension does not grow
unbounded?
Per-User caching does seem to be something that is going to be needed...
Depending on how many users are being tracked would storing the "reader_id"
in an indexed array improve matters? " SELECT ... FROM message WHERE NOT (1
= ANY(reader_ids)) ; UPDATE message SET reader_ids = reader_ids || 1 WHERE
messageid = ..." I'm not that familiar with how well indexes over arrays
work or which kind is needed (i.e. gin/gist).
HTH
David J.
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