Re: Optimize query for listing un-read messages

På fredag 02. mai 2014 kl. 00:55:25, skrev David G Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com <mailto:david(dot)g(dot)johnston(at)gmail(dot)com>>: 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?     No, unfortunately...   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).     "is_read" is one of many
properties being tracked for a message...   -- Andreas Jospeh Krogh CTO /
Partner - Visena AS Mobile: +47 909 56 963 andreas(at)visena(dot)com
<mailto:andreas(at)visena(dot)com> www.visena.com <https://www.visena.com>
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