Re: Fragmenting tables/indexes

Posted in 1997

Clem Akins — 14 Oct 1997 00:58:05 -0400 — source: Informix-list mailing list archive (1991-1998)

Cosmo advises: >Are you sure that your queries are _actually_ using the fragments to >eliminate data from the searches? We had a similar situation where data >was fragmented by dates. But when we ran certain queries, the optimizer >ignored the fragmentation scheme altogether, performing searches of all >fragments when it should have been able to eliminate subsets of data. Be sure that your understanding matches what the optimiser is built to do. It is easy to get out of sync there, as the rules for fragment elimination are not terribly straightforward. See the OnLine Performance Guide, page 3-49 (in my 7.22 CD-ROM version.) And to reinforce what Cosmo says: see the query plan with SET EXPLAIN to know for sure what the optimiser is doing. ___________________________________________________________ Clem Akins (aka clem@informix.com) <- NEW ACCOUNT! Informix Software, Inc (Standard disclaimers apply) International Technical Support Last seen: Corporate HQ, Menlo Park California, US of A