Hi, This is not going to answer your question of course but did you already try to do this in 2 steps?
You said that the subquery itself doesn't take very long, so perhaps you can create a temporary table based on the subquery, then in the update do a join with the temporary table? This might not be desirable in the end, but it might be useful just to check the performance of it. And - isn't it an option to upgrade to 7.4.1 instead? regards, --Tim THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Eric Jain Sent: dinsdag 17 februari 2004 13:38 To: pgsql-performance Subject: [PERFORM] UPDATE with subquery too slow I can't get the following statement to complete with reasonable time. I've had it running for over ten hours without getting anywhere. I suspect (hope) there may be a better way to accomplish what I'm trying to do (set fields containing unique values to null): UPDATE requests SET session = NULL WHERE session IN ( SELECT session FROM requests GROUP BY session HAVING COUNT(*) = 1 ); [...] ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
