On Tue, May 16, 2006 at 07:08:51PM -0700, David Wheeler wrote: > On May 16, 2006, at 18:29, Christopher Kings-Lynne wrote: > > >>Yes, but there are definitely programming cases where memoization/ > >>caching definitely helps. And it's easy to tell for a given > >>function whether or not it really helps by simply trying it with > >>CACHED and without. > >>Would this be a simple thing to implement? > > > >It's called a "table" :) > > http://www.justatheory.com/computers/databases/postgresql/ > higher_order_plpgsql.html > > Yes, I know. :-P But it'd be easier to have a CACHED keyword, of course.
Rather than worrying about a generic form of memoization, what would be extremely valuable would be to improve detection of the same function being used multiple times in a query, ie: SELECT moo(x), moo(x)/2 FROM table; AFAIK PostgreSQL will currently execute moo(x) twice. Even if it knows how to optimize this brain-dead example, I think there are other examples it can't optimize right now. Having a much simpler memoization scheme that only works on a tuple-by-tuple basis would probably eliminate a lot of those (It wouldn't work for any executor node that has to read it's entire input before returning anything, though, such as sort). -- 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 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
