On Wed, Jul 19, 2006 at 07:54:49PM -0400, Tom Lane wrote: > "Jim C. Nasby" <[EMAIL PROTECTED]> writes: > > Indeed, if I find a case where there's a large enough number of rows it > > will choose the smaller index. But I'm wondering if it would be better > > to always favor the smaller index, since it would (presumably) be easier > > to keep it in cache? > > AFAICS, in existing releases that should happen, because the cost > estimate varies with the size of the index. And it does happen for me > in simple tests. You did not provide the requested information to help > us find out why it's not happening for you. > > (I'm a bit worried about whether CVS HEAD may have broken this behavior > with the recent changes in the indexscan cost equations ... but unless > you are working with HEAD that's not relevant.)
No, this is 8.1.3, and it's a production machine so I'd prefer not to go about dropping indexes to get cost comparisons; unless there's some way to disable the use of an index in a given backend? Otherwise I'll try and come up with a test case. -- Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
