Robert Haas <robertmh...@gmail.com> writes: > On Wed, Jan 26, 2011 at 3:08 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Robert Haas <robertmh...@gmail.com> writes: >>> It's not obvious to me that it has a use case outside of casts, but >>> it's certainly possible I'm missing something.
>> A possible example is simplifying X + 0 to X, or X * 0 to 0. > Oh, I see. The times I've seen an issue with those kinds of > expressions have always been related to selectivity estimation. Yeah, helping the planner recognize equivalent cases is at least as large a reason for wanting this as any direct savings of execution time. I don't mind confining the feature to casts to start with, but it might be a good idea to specify the check-function API in a way that would let it be plugged into a more generally available call-simplification hook later. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers