Michael Graham <mgraham@xxxxxxxxx> writes: > I was playing around with some sql in postgres and got to wondering why > the optimiser can't figure out that rearranging some expressions can > result in massive improvements in the queue plan. For example id + 5 < > 100 compared with id < 100 - 5. > Is it simply that no one has go around to doing it or is there some > deeper reasons? It's not really important I'm just curious. Well, it'd require a very large amount of type-specific/operator-specific knowledge, and it's not clear what would drive the planner towards doing useful rearrangements rather than counterproductive ones, and the number of real-world queries where it'd actually help doesn't seem to be that large. I've seen one or two complaints about that sort of thing, but it's way way down the list of serious problems. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
