Alban Hertroys wrote: > I have a query here for which postgres chooses a nested loop, for which > it takes ~19s to complete in the worst-case (measured). However, if I > disable nestloops it completes in ~400ms... > > It seems pretty obvious that the planner underestimates the cost of > nestloops here, is there some way to tweak this? Ok, I think I've figured this one out. A few order by's after the groups in my subqueries helped a _lot_. I'm now back under 1s again. > This is using PostgreSQL 8.1.4 on x86_64-pc-linux-gnu, compiled by GCC > cc (GCC) 3.3.5 (Debian 1:3.3.5-13) > > The server is on some kind of xen domain. I have absolutely no idea what > impact that has for various planner parameters (except that it'll > probably not perform as well as an unxenned server), it may be relevant. > > The plans with and w/o nestloops respectively are attached (to prevent > wrapping). > > > > ------------------------------------------------------------------------ > > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings -- Alban Hertroys alban@xxxxxxxxxxxxxxxxx magproductions b.v. T: ++31(0)534346874 F: ++31(0)534346876 M: I: www.magproductions.nl A: Postbus 416 7500 AK Enschede // Integrate Your World //
