On Wed, Apr 30, 2008 at 8:16 PM, Tom Lane <[EMAIL PROTECTED]> wrote: > "Pavan Deolasee" <[EMAIL PROTECTED]> writes: > > That's weird. With that fillfactor, you should have a very high > > percentage of HOT update ratio. It could be a very special case that > > we might be looking at. > > He's testing >
It's "She" :-) Oh yes. Apologies if I sounded harsh; did not mean that. I was just completely confused why she is not seeing the HOT updates. > >> update table1 set delta1 = 100 where code/1000000 =999; > > so all the rows being updated fall into a contiguous range of "code" > values. If the table was loaded in such a way that those rows were > also physically contiguous, then the updates would be localized and > would very soon run out of freespace on those pages. > Yeah, that seems like the pattern. I tested with the similar layout and a fill factor 80. The initial few bulk updates had comparatively less HOT updates (somewhere 20-25%), But within 4-5 iterations of updating the same set of rows, HOT updates were 90-95%. That's because after few iterations (and because of non-HOT updates) the tuples get scattered in various blocks, thus improving chances of HOT updates. I guess the reason probably is that she is using fill factor for indexes and not heap, but she hasn't yet confirmed. 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
