Tom Lane wrote: > Jeff Janes <jeff.ja...@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.
Plus kernel read-ahead helps with sequential access too because the kernel can guess the next blocks to be requested --- hard to do that with random I/O. SSD have fast access but still benefit from read-ahead. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
