Ron Mayer <[EMAIL PROTECTED]> writes: > I'm wildly guessing that, the # of pages itself seems to be > a bigger factor than the sequential/random nature.
No, they're both important: fetching N pages in sequence is way cheaper than fetching the same number of pages scattered all over. This is partly because you reduce seeking at the hardware level, and partly because sequential reads cue the kernel to do read-ahead, allowing overlap of I/O and computation. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq