On Thursday 13 October 2005 16:06, Tom Lane wrote: > > You'd have to change the source code, but it's a simple tweak in the > ALTER SET STATISTICS code. > I don't think I'd want to do that.
> > If the only penalty is slower analyzing, I don't care: we analyze at > > night when these system are idle. > > You'd be wrong about that --- the planner operations that use the data > would necessarily be slower, too. I don't have any concrete information > about how much slower, but I'd be hesitant to raise the figure much > beyond 1000 ... > > However, if you can show you have a real-world case that benefits, I'd > be willing to think about raising the wired-in limit to 10000 or so. > The example I gave earlier in the thread, date_of_birth = 'some-date' and surname like 'blaa%', was a real life example, but I had to pull it from a logfile that logs queries longer than 500 ms. It happens two or three times a day in a laboratory with 50 people querying the database all day. Estimates for date_of_birth number of rows are quite good (even at the default stats of 10) but surnames are just too unevenly distributed. But in 99% of all cases the guess is right, and by making it a nested query I could improve 1% and worsen 99%. Cheers, Han Holl ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
