On 10/10/2010 8:27 PM, Joshua Tolley wrote:
It was asserted that reading bigger chunks would help performance; a response suggested that, at least in Linux, setting readahead on a device would essentially do the same thing. Or that's what I got from the thread, anyway. I'm interested to know how similar performance might be between the large block size case and the large readahead case. Comments, anyone?
Craig maybe right, the fact that Oracle is doing direct I/O probably does account for the difference. The fact is, however, that the question about slow sequential scan appears with some regularity on PostgreSQL forums. My guess that a larger chunk would be helpful may not be correct, but I do believe that there is a problem with a too slow sequential scan. Bigger chunks are a very traditional solution which may not work but the problem is still there.
-- Mladen Gogala Sr. Oracle DBA 1500 Broadway New York, NY 10036 (212) 329-5251 www.vmsinfo.com -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
