Re: Optimize query for listing un-read messages

På torsdag 01. mai 2014 kl. 21:53:32, skrev Pavel Stehule <
pavel(dot)stehule(at)gmail(dot)com <mailto:pavel(dot)stehule(at)gmail(dot)com>>:     2014-05-01 21:39
GMT+02:00 Andreas Joseph Krogh<andreas(at)visena(dot)com <mailto:andreas(at)visena(dot)com>>:
På torsdag 01. mai 2014 kl. 21:30:39, skrev Pavel Stehule <
pavel(dot)stehule(at)gmail(dot)com <mailto:pavel(dot)stehule(at)gmail(dot)com>>: Hello [snip]   I had
a perfect success on similar use case with descent ordered partial index

http://www.postgresql.org/docs/9.3/interactive/sql-createindex.html
<http://www.postgresql.org/docs/9.3/interactive/sql-createindex.html>   I'm not
getting good performance. Are you able to craft an example using my schema and
partial index?   maybe some like
  CREATE INDEX ON message_property (person_id, message_id) WHERE pr.is_read
  When I am thinking about your schema, it is designed well, but it is not
index friendly, so for some fast access you should to hold a cache (table) of
unread messages   Ah, that's what I was hoping to not having to do. In my
system, messages arrive all the time and having to update a cache for all new
messages for all users seems messy... Seems I could just as well create a
message_property for all users when a new message arrives, so I can INNER JOIN
it and get good performance. But that table will quickly grow *very* large...  
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