"Steinar H. Gunderson" <[EMAIL PROTECTED]> writes: > Now, my first notion was creating a functional index to help the planner: > ... > However, this obviously didn't help the planner (this came as a surprise to > me, but probably won't come as a surprise to the more seasoned users here :-)
7.4 doesn't have any statistics on expression indexes. 8.0 will do what you want though. (I just fixed an oversight that prevented it from doing so...) > Actually, it seems that the higher I set statistics on "tid", the worse the > estimate becomes. I believe that the estimate of number of groups will be exactly the same as the estimate of the number of values of tid --- there's no knowledge that date_trunc() might reduce the number of distinct values. > Any ideas for speeding this up? In 7.4, the only way I can see to force this to use a hash aggregate is to temporarily set enable_sort false or raise sort_mem. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings