On Wed, Apr 30, 2008 at 8:16 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "Pavan Deolasee" <pavan.deolasee@gmail.com> 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