Tom, your suspicions were correct - ANALYZE was not being run. I run vacuumdb via a cron script during off hours. After checking the scripts on both systems, I found that on the system that was not functioning correctly that the '-z' (analyze) command line option to vacuumdb was missing. After correcting it and re-running the script, the poorly performing SQL query takes only a few seconds as opposed to 15 minutes.
Thank you for your help! - David -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Tom Lane Sent: Wednesday, August 25, 2004 3:08 PM To: Richard Huxton Cc: David Price; [EMAIL PROTECTED] Subject: Re: [PERFORM] Optimizer Selecting Incorrect Index Richard Huxton <[EMAIL PROTECTED]> writes: > Things to check: > 1. postgresql.conf settings match - different costs could cause this > 2. statistics on the two columns (trn_patno,trn_old_date) - if they > differ considerably between systems that would also explain it. The different estimated row counts could only come from #2. I suspect David has forgotten to run ANALYZE on the second system. I agree that EXPLAIN VERBOSE output is not helpful... regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
