Brian Herlihy <btherl@xxxxxxxxxxxx> writes: > What would it take for hints to be added to postgres? A *whole lot* more thought and effort than has been expended on the subject to date. Personally I have no use for the idea of "force the planner to do exactly X given a query of exactly Y". You don't have exactly Y today, tomorrow, and the day after (if you do, you don't need a hint mechanism at all, you need a mysql-style query cache). IMHO most of the planner mistakes we see that could be fixed via hinting are really statistical estimation errors, and so the right level to be fixing them at is hints about how to estimate the number of rows produced for given conditions. Mind you that's still a plenty hard problem, but you could at least hope that a hint of that form would be useful for more than one query. regards, tom lane
