> On Saturday 14 July 2001 02:49, Tom Lane wrote: > > > > > > > It would seem that Oracle's execution plan is more optimal. > > > > Hmm, since I don't know the details of Oracle's plan displays, it's hard > > to comment on that --- but it looks to me like the plans are essentially > > the same, with the small difference that Postgres chooses to use the > > index on dim0 to filter ....(snipped ) > > After a little thinking, I am inclined to agree with you Tom... I wondered if > the difference might to be due to pure sequential scan performance > differences. I tried this query : > > SELECT sum(val) FROM fact0 > > for Postgres, Db2 and Oracle. The results were > > Postgres 2m25s > Db2 40s > Oracle 50s > > This seems to be the likely culprit. I suspect that the "many block/page read > at once" type optimzations (prefetch for Db2 and mutli block read for Oracle) > mean that table sequential scans are faster for these guys than Postgres. > > Thus on the bright side their access plans are not necessarily any better > than Postgres ! Can you remind me about the OS you are using? -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
