On Fri, Jan 13, 2006 at 11:37:38PM -0500, Tom Lane wrote: > Josh Berkus <josh@agliodbs.com> writes: > >> It's also worth mentioning that for datatypes that only have an "=" > >> operator the performance of compute_minimal_stats is O(N^2) when values > >> are unique, so increasing sample size is a very bad idea in that case. > > > Hmmm ... does ANALYZE check for UNIQUE constraints? > > Our only implementation of UNIQUE constraints is btree indexes, which > require more than an "=" operator, so this seems irrelevant.
IIRC, the point was that if we know a field has to be unique, there's no sense in doing that part of the analysis on it; you'd only care about correlation. -- 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 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
