On Sat, Jul 12, 2008 at 2:25 AM, Roberts, Jon <Jon.Roberts@asurion.com> wrote:
>>
>> --
>
> I can find very little information on hot updates but I found this:
http://archives.postgresql.org/pgsql-patches/2006-11/msg00059.php
>
> It states, "This design optimizies the updates when none of the index columns are modified and length of the tuple
remainsthe same after update."
>
> How can a row's length change? I think it must mean the size (in bytes) of the row remains the same.
>
I bet you are looking at an old design. That has undergone many
changes and the current implementation does not have any restriction
about the row length changes. But a necessary condition is to have
enough free space in the block (and of course not changing any index
columns).
You can find the latest README in the source code under
src/backend/access/heap/README.HOT
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com