2009/10/14 Thom Brown <thombr...@gmail.com>: > 2009/10/14 Scott Marlowe <scott.marl...@gmail.com>: >> >> If what you're trying to do is emulate a real world app which randomly >> grabs rows, then you want to setup something ahead of time that has a >> pseudo random order and not rely on using anything like order by >> random() limit 1 or anything like that. Easiest way is to do >> something like: >> >> select id into randomizer from maintable order by random(); >> >> then use a cursor to fetch from the table to get "random" rows from >> the real table. >> >> > > Why not just do something like: > > SELECT thisfield, thatfield > FROM my_table > WHERE thisfield IS NOT NULL > ORDER BY RANDOM() > LIMIT 1; >
this works well on small tables. On large tables this query is extremely slow. regards Pavel > Thom > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance > -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
