On Mon, Jun 26, 2006 at 11:08:24PM -0400, Bruce Momjian wrote: > Jim C. Nasby wrote: > > On Mon, Jun 26, 2006 at 02:32:59PM -0400, Bruce Momjian wrote: > > > > > > It is certainly possible to do what you are suggesting, that is have two > > > index entries point to same chain head, and have the index access > > > routines figure out if the index qualifications still hold, but that > > > seems like a lot of overhead. > > > > > > Also, once there is only one visible row in the chain, removing old > > > index entries seems quite complex because you have to have vacuum keep > > > the qualifications of each row to figure out which index tuple is the > > > valid one (seems messy). > > > > Perhaps my point got lost... in the case where no index keys change > > during an update, SITC seems superior in every way to my proposal. My > > idea (let's call it Index Tuple Page Consolidation, ITPC) would be > > beneficial to UPDATEs that modify one or more index keys but still put > > the tuple on the same page. Where SITC would be most useful for tables > > that have a very heavy update rate and very few indexes, ITPC would > > benefit tables that have more indexes on them; where presumably it's > > much more likely for UPDATEs to change at least one index key (which > > means SITC goes out the window, if I understand it correctly). If I'm > > missing something and SITC can in fact deal with some index keys > > changing during an UPDATE, then I see no reason for ITPC. > > I understood what you had said. The question is whether we want to get > that complex with this feature, and if there are enough use cases > (UPDATE with index keys changing) to warrant it.
Ideas on how to test a table to see how many tuples would fit this criteria? Or we could just shelve ITPC as a possibility in the future, after we see how much the limitations of SITC hurt. -- 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 6: explain analyze is your friend