Dimitri Fontaine <dimi...@2ndquadrant.fr> writes: > Looks like we're missing out some operator properties, like the neutral > element and if the operator is transitive, commutative or associative. I > think I remember us talking about how knowing about operators being > associative would also help optimize a class of join problems.
We do understand, and use, transitivity for btree equality operators (cf mergejoin planning, EquivalenceClasses, etc). I have limited enthusiasm for introducing a more general concept, because it seems like doing anything with it would add a great deal more planning effort for (typically) little reward. I can imagine cases where, say, deducing "a < c" from "a < b and b < c" would be helpful ... but they don't come up in common queries. 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