Jeff Janes <jeff.janes@gmail.com> writes:
> Of course if you do a full table scan because their are no better
> options, then it scans sequentially. But you have to scan the pages
> in *some* order, and it is hard to see how something other than
> sequential would be systematically better.
In fact, if sequential *isn't* the best order for reading the whole
file, the filesystem has lost its marbles completely; because that is
the order in which most files are read, so files ought to be laid out
on disk (or whatever storage device) to be read most quickly that way.
regards, tom lane