On Mon, Mar 24, 2008 at 3:37 PM, Andreas Kretschmer <[EMAIL PROTECTED]> wrote: > petchimuthu lingam <[EMAIL PROTECTED]> schrieb: > > > > Hi friends, > > > > I am using postgresql 8.1, I have shared_buffers = 50000, now i execute the > > query, it takes 18 seconds to do sequential scan, when i reduced to 5000, > it > > takes one 10 seconds, Why. > > Wild guess: the second time the data are in the filesystem cache. >
Another wild possibility is that the first query sets the hint bits for the rows involved and hence the second time it runs fast. May be you want to run the query few times in both the settings and then compare. Thanks, Pavan -- Pavan Deolasee EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
