Re: Online 7.11 Select Performance - Odd Results

On Nov 29, 17:10, Nick Nobbe wrote: > > Clay, > My experience, too. When you use the last part of a concatenated > key, i.e. 3 of index(1,2,3), the performance is a doggie. There's a performance dog, but a select that takes over ten minutes on a dedicated 4-processor HP with 512MB of memory and completely shuts down the TCP pipe is not what I call a dog -- I call it "broken". :) > So things hum when you use all three, or the first two, or the > first one, and I suspect you're getting good results when you > select on all three columns for the same reason, but to get a > clear picture of what's happening, > > set explain on; > select .... , etc.> > then read the explain.out diagnostic file in the current directory. We looked at this. The select that kills system is a sequential scan, and I believe a temp table is created, but still -- 10 minutes? > Off the top of my head, y'all forgive me for shooting my bandwith > off, a kluge might be > select x > from your_table > where col1 is not null (if it's key it can't be, but so what) > and col2 is not null > and col3 = something;> > Anyway, don't give up. There's usually a way. I appreciate your comments. I'll give this select a try and see what happens. Thanks. -- Clay Irving, N2VKG clay@panix.com http://www.panix.com/clay