On Fri, Jan 06, 2006 at 02:48:59PM -0500, Tom Lane wrote: > "Jim C. Nasby" <[EMAIL PROTECTED]> writes: > > Is caching of results for STABLE/IMMUTABLE functions called with a > > constant something that would be reasonable to add? > > I tend to think not: the distributed overhead would outweigh the > advantages. See previous discussions in the archives. > > (However, the previous discussions have imagined an explicit cache > that stores function names, arguments, and results. Your thought > of transforming the call into an InitPlan node might be interesting. > The trick is still to know which functions are expensive enough to > justify the overhead of an InitPlan.) >
Oh, yeah, actually caching results between queries doesn't make sense; I think that's pretty much a corner-case that people should be expected to code up/handle themselves. I'm just looking for only executing the function once per query. Yeah, some heuristics to try and tweak between adding a seperate planning node and just running the function a few times would be nice, but I suspect that's overkill. I think it would be fine to just assume that any time you're going to execute a function more than X number of times (where X should be easy to deduce during query planning), you'll be better off taking the cost to tweak the plan to only run it once. How does the overhead of an InitPlan compare to the overhead of calling a SQL function? Or plpgsql? Or one of the external function languages? -- 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
