On Wed, Feb 22, 2012 at 2:23 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > The industry accepted description for non-sequential access is "random > access" whether or not the function that describes the movement is > entirely random. To argue otherwise is merely hairsplitting.
I don't think so. For example, a bitmap index scan contrives to speed things up by arranging for the table I/O to happen in ascending block number order, with skips, rather than in random order, as a plain index scan would do, and that seems to be a pretty effective technique. Except to the extent that it interferes with the kernel's ability to do readahead, it really can't be to read blocks 1, 2, 3, 4, and 5 than to read blocks 1, 2, 4, and 5. Not reading block 3 can't require more effort than reading it. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers