Re: Optimize query for listing un-read messages

På fredag 02. mai 2014 kl. 01:58:04, skrev David G Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com <mailto:david(dot)g(dot)johnston(at)gmail(dot)com>>:
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...     ​But you don't have to have all
of them on the same table.  Once you've identified the messages in question
performing a standard join onto a supplemental detail table should be fairly
straight-forward.   Do these other properties have values when "is_read" is
false or only when "is_read" is true?  Since you already allow for the
possibility of a missing record (giving it the meaning of "not read")​ these
other properties cannot currently exist in that situation.     A message might
hold a property (ie. is_important) when is_read is FALSE (it might be set back
to is_read=FALSE after being read the first time).   -- 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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