On Tue, Aug 16, 2016 at 2:43 AM, Alexander Korotkov <a.korot...@postgrespro.ru> wrote:g of pg_operator.oprassociative... > Another problem is computational complexity of such transformations. AFAIR, > few patches for making optimizer smarter with expressions were already > rejected because of this reason.
s/few/many/ > Also, even if we would have such transformation of expressions, floating > points types would be still problematic, because (a + b) + c = a + (b + c) > is not exactly true for them because of computational error. Right. I think matching expressions exactly is plenty good enough. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers