OK, what you are seeing here is that for your platform the TESTCYCLES size isn't enough; the numbers are too close to measure the difference.
I am going to increase the TESTCYCLES from 5k to 10k. That should provide better numbers. --------------------------------------------------------------------------- Oliver Elphick wrote: > On Mon, 2002-09-09 at 07:13, Bruce Momjian wrote: > > > > OK, turns out that the loop for sequential scan ran fewer times and was > > skewing the numbers. I have a new version at: > > > > ftp://candle.pha.pa.us/pub/postgresql/randcost > > Latest version: > > olly@linda$ > random test: 14 > sequential test: 11 > null timing test: 9 > random_page_cost = 2.500000 > > olly@linda$ for a in 1 2 3 4 5 > > do > > ~/randcost > > done > Collecting sizing information ... > random test: 11 > sequential test: 11 > null timing test: 9 > random_page_cost = 1.000000 > > random test: 11 > sequential test: 10 > null timing test: 9 > random_page_cost = 2.000000 > > random test: 11 > sequential test: 11 > null timing test: 9 > random_page_cost = 1.000000 > > random test: 11 > sequential test: 10 > null timing test: 9 > random_page_cost = 2.000000 > > random test: 10 > sequential test: 10 > null timing test: 10 > Sequential time equals null time. Increase TESTCYCLES and rerun. > > > Available memory (512M) exceeds the total database size, so sequential > and random are almost the same for the second and subsequent runs. > > Since, in production, I would hope to have all active tables permanently > in RAM, would there be a case for my using a page cost of 1 on the > assumption that no disk reads would be needed? > > -- > Oliver Elphick [EMAIL PROTECTED] > Isle of Wight, UK > http://www.lfix.co.uk/oliver > GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839 932A 614D 4C34 3E1D 0C1C > ======================================== > "Draw near to God and he will draw near to you. > Cleanse your hands, you sinners; and purify your > hearts, you double minded." James 4:8 > > -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
