On Tue, 9 Nov 2004, Tom Lane wrote:
Awhile back, there was some discussion about pre-folding now() and related functions when the planner is trying to estimate selectivities. This would allow reasonable plans to be made for cases like WHERE moddate >= current_date - 10; without having to indulge in any crude hacks with mislabeled wrapper functions, such as you can find all too often in the archives :-(
I was a bit hesitant about it at the time because I wasn't sure of all the implications; but I've looked the idea over again, and as far as I can see it's reasonable to pre-fold *all* stable functions when deriving statistical estimates. (One of the potential objections went away when we started enforcing that stable functions don't have side-effects.)
The infrastructure for this is already there, because of Oliver Jowett's previous work to teach eval_const_expressions() whether it's folding the expression "for real" or just for estimation; it's basically a one line change to treat stable functions differently in the two cases.
I know it's a bit late in the cycle, but I'd like to go ahead and make this change for 8.0. Objections?
From a performance tuning standpoing, I can't argue against it ... go for
it ...
---- Marc G. Fournier Hub.Org Networking Services (http://www.hub.org) Email: [EMAIL PROTECTED] Yahoo!: yscrappy ICQ: 7615664
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