The fact that an index exists adds a choice -- so by no means is the index ignored.
But just because a Freeway exists across town doesn't make it faster than the sideroads. It depends on the day of week, time of day, and uncontrollable anomolies (accidents). -- Rod Taylor Your eyes are weary from staring at the CRT. You feel sleepy. Notice how restful it is to watch the cursor blink. Close your eyes. The opinions stated above are yours. You cannot imagine why you ever felt otherwise. ----- Original Message ----- From: "mlw" <[EMAIL PROTECTED]> To: "Thomas Lockhart" <[EMAIL PROTECTED]> Cc: "Tom Lane" <[EMAIL PROTECTED]>; "Bruce Momjian" <[EMAIL PROTECTED]>; "Louis-David Mitterrand" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Wednesday, April 17, 2002 10:31 AM Subject: Re: [HACKERS] Index Scans become Seq Scans after VACUUM ANALYSE > Thomas Lockhart wrote: > > Systems which have optimizing planners can *never* be guaranteed to > > generate the actual lowest-cost query plan. Any impression that Oracle, > > for example, actually does do that may come from a lack of visibility > > into the process, and a lack of forum for discussing these edge cases. > > And here in lies the crux of the problem. It isn't a purely logical/numerical > formula. It is a probability estimate, nothing more. Currently, the statistics > are used to calculate a probable best query, not a guaranteed best query. The > presence of an index should be factored into the probability of a best query, > should it not? > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED] > ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
