Le 09/11/2011 08:12, Ian Booth a écrit : > Hi > > Let me rephrase the question - for a simple count of owned branches, I > can't see a need to do all the stuff shown in the queries on the timeout > oops. I mean, selecting the entire column set from the query table(s) > just to do a count(*) on the rows returned seems pretty dumb, and I'd be > surprised if there weren't performance issues like those we are seeing > on large result sets. > > So, I still wonder whether > a) > select count(*) from branch > where branch.owner in ( > select team from teamparticipation where person = %d) > is really that expensive, and
Well, this is a more complex query than the one you suggest here but if you take a look at the query/explain analyse below, you will see that the expensive part is the Seq scan that owner=XXX and NOT transitively_private generates. Having looked at this with jtv and lifeless it seems that there is now way to have this count query performing well. The query: https://pastebin.canonical.com/54885/ The EXPLAIN ANALYSE: https://pastebin.canonical.com/54886/ _______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : launchpad-dev@lists.launchpad.net Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
