mlw wrote: > Bruce Momjian wrote: > > > > > OK, yes, sequential scan _can_ be as slow as index scan, but sometimes > > it is faster. Can you provide reasoning why index scan should be > > preferred, other than the admin created it, which I already addressed? > > If you have a choice between two or more sub-plans, similar in cost, say within > 20% of one another. Choosing a plan which uses an index has a chance of > improved performance if the estimates are wrong where as choosing the > sequential scan will always have the full cost.
And the chance of reduced performance if the estimate was too low. -- 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
