On Tue, Feb 24, 2015 at 2:20 PM, Peter Eisentraut <pete...@gmx.net> wrote: > On 2/20/15 3:09 PM, Tomas Vondra wrote: >> The 'combine' function gets two such 'state' values, while transition >> gets 'state' + next value. > > I think the combine function is not actually a property of the > aggregate, but a property of the transition function. If two aggregates > have the same transition function, they will also have the same combine > function. The combine function really just says, how do you combine two > series of these function calls. Say maybe this should be put into > pg_proc instead. (Or you make the transition functions transition > operators and put the info into pg_operator instead, which is where > function call optimization information is usually kept.)
This seems like a weird design to me. It's probably true that if the transition function is the same, the state-combiner function will also be the same. But the state-combiner function is only going to exist for aggregate transition functions, not functions or operators in general. So linking it from pg_proc or pg_operator feels wrong to me. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
