On Mar 24, 2011, at 5:23 PM, Claudio Freire wrote: > I routinely have to work around query inefficiencies because GEQO does > something odd - and since postgres gives me too few tools to tweak > plans (increase statistics, use subqueries, rephrase joins, no direct > tool before CTEs which are rather new), it becomes an art form, and it > becomes very unpredictable and an administrative burden. Out of the > blue, statistics change, queries that worked fine start to perform > poorly, and sites go down. > > If GEQO could detect unsafe plans and work around them automatically, > it would be a major improvement.
This isn't limited to GEQO queries either. Every few months we'll have what should be a very fast query suddenly become far slower. Still on the order of seconds, but when you're running several of those a second and they normally take fractions of a second, this kind of performance degradation can easily bring a server to it's knees. Every time this has happened the solution has been to re-analyze a fairly large table; even with default stats target of 1000 it's very easy for one bad analyze to ruin your day. -- Jim C. Nasby, Database Architect j...@nasby.net 512.569.9461 (cell) http://jim.nasby.net -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
