On Thu, 2005-04-14 at 12:10 -0400, Tom Lane wrote: > The first of these should of course force a btree split on the first > page each time it splits, while the second will involve the > probabilistic moveright on each split. But the files will be exactly > the same size. > > [EMAIL PROTECTED] ~]$ time psql -f zdecr10 test > TRUNCATE TABLE > > real 1m41.681s > user 0m1.424s > sys 0m0.957s > [EMAIL PROTECTED] ~]$ time psql -f zsame10 test > TRUNCATE TABLE > > real 1m40.927s > user 0m1.409s > sys 0m0.896s > [EMAIL PROTECTED] ~]$
I think thats conclusive. > So the theory does work, at least for small index entries. Currently > repeating with wider ones ... I think we should adjust the probability for longer item sizes - many identifiers can be 32 bytes and there are many people with a non-unique URL column for example. An average of over 2 blocks/insert at 16 bytes is still one too many for my liking, though I do understand the need for the randomness. I'd suggest a move right probability of 97% (divide by 16) for itemsz > 16 bytes and 94% (divide by 32) when itemsz >= 128 Though I think functional indexes are the way to go there. Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
