Palle Girgensohn <[EMAIL PROTECTED]> writes: > When running > select max("when") from login where userid='userid' > it takes a second or two, but when adding "group by userid" the planner > decides on using another plan, and it gets *much* faster. See example below.
It's only faster for cases where there are few or no rows for the particular userid ... > Number of tuples per user varies from zero to a couple of thousands. The planner is using an intermediate estimate of 406 rows. You might be well advised to increase the statistics target for login.userid --- with luck that would help it to choose the right plan type for both common and uncommon userids. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq