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On 2011-05-16 03:18, Greg Smith wrote: > You can't do it in real-time. You don't necessarily want that to > even if it were possible; too many possibilities for nasty feedback > loops where you always favor using some marginal index that happens > to be in memory, and therefore never page in things that would be > faster once they're read. The only reasonable implementation that > avoids completely unstable plans is to scan this data periodically > and save some statistics on it--the way ANALYZE does--and then have > that turn into a planner input. Would that be feasible? Have process collecting the data every now-and-then probably picking some conservative-average function and feeding it into pg_stats for each index/relation? To me it seems like a robust and fairly trivial way to to get better numbers. The fear is that the OS-cache is too much in flux to get any stable numbers out of it. -- Jesper |
