On Tue, Sep 27, 2005 at 10:24:02AM +0200, Csaba Nagy wrote: > Hi all, > > I've recently asked a similar question, which received no useful answer > yet, so I'll drop in too. > > In my case, the table I was inserting to was a quite big one already to > start with (and analyzed so), so I was expecting that it will not slow > down due to indexes, as they were quite big to start with as I said. > > What I mean is that I expected that the speed will be more or less > constant over the whole inserting. But the result was that after a while > the average insert speed dropped considerably and suddenly, which I > can't explain and would like to know what caused it... > The table was ~100 million live rows and quite often updated, and the > insert was ~40 million rows. After ~10 million rows the average speed > dropped suddenly about 4 times. > > My only suspicion would be that the table had a quite big amount of free > space in it at the beginning due to the fact that it is quite often > updated, and then the free space was exhausted. So the speed difference > might come from the difference in using free space versus creating new > pages ? Or the same thing for the b-tree indexes. > > Is there any other reasonable explanation for this ? As I see this kind > of behavior consistently, speed OK on start of inserting, and then slow > down, and I would like to know if I can tune my DB to cope with it or > just accept that it works like this... > > Cheers, > Csaba. I can't think of any explanation for this off-hand. Can you re-run the test on a table that doesn't have a bunch of free space in it to see if that's what the issue was? -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
