| From: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | "Adam Rich" <adam(dot)r(at)sbcglobal(dot)net> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: 8.3.0 upgrade |
| Date: | 2008-03-17 12:27:36 |
| Message-ID: | 2e78013d0803170527m376bafa1n1152e329365267e9@mail.gmail.com |
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| Thread: | |
| Lists: | pgsql-general |
On Mon, Mar 17, 2008 at 12:43 PM, Adam Rich <adam(dot)r(at)sbcglobal(dot)net> wrote:
>
> Finally, regarding the new "HOT" feature. The release notes say that
> benefits are realized "if no changes are made to indexed columns".
> If my updates include *all columns* (the SQL is generated dynamically)
> but the new value matches the old value for all *indexed* columns,
> do I still reap the benefits of HOT?
>
Yes. At the execution time, a binary comparison of old and new index
column values is performed and if the old and new value is same for
all index columns, HOT update is feasible. So even if the UPDATE statement
sets value to one of the index columns, HOT update is possible as
long as the old and the new value is same.
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
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