Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> Recently there was a post on -performance about a particular case where
> Postgres doesn't make very good use of the I/O system. This is when you try to
> fetch many records spread throughout a table in random order.
> http://archives.postgresql.org/pgsql-performance/2007-12/msg00005.php
Since the OP in that thread has still supplied zero information
(no EXPLAIN, let alone ANALYZE, and no version info), it's pure
guesswork as to what his problem is.
regards, tom lane