On Mon, May 08, 2006 at 10:42:21AM -0700, Mark Lewis wrote: > Doing a SELECT with a large list of variables inside an IN runs slowly > on every database we've tested. We've tested mostly in Oracle and > PostgreSQL, and both get very slow very quickly (actually Oracle refuses > to process the query at all after it gets too many bind parameters). > > In our case, we have a (potentially quite large) set of external values > that we want to look up in the database. We originally thought that > doing a single select with a large IN clause was the way to go, but then > we did some performance analysis on the optimal batch size (number of > items to include per IN clause), and discovered that for most databases, > the optimal batch size was 1. For PostgreSQL I think it was 2. > > The moral of the story is that you're probably better off running a > bunch of small selects than in trying to optimize things with one > gargantuan select. Ever experiment with loading the parameters into a temp table and joining to that? -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
