"Mikko Partio" <mpartio(at)gmail(dot)com> writes: > I guess the sort_mem helped, or then part of the rows are in the cache > already. Should increasing sort_mem help here since there are no sorts etc?
No, it wouldn't --- this change has to be due to the data being already loaded into cache.
There's no obvious reason for the previous query to be so slow, unless you've got horrendously slow or overloaded disk hardware. What sort of machine is this anyway, and was it doing any other work at the time?