| From: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | "Zdenek Kotala" <Zdenek(dot)Kotala(at)sun(dot)com> |
| Cc: | "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: visibility maps |
| Date: | 2008-12-11 13:41:16 |
| Message-ID: | 2e78013d0812110541tb80aea1sd8a03dee9b890534@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Dec 11, 2008 at 7:03 PM, Zdenek Kotala <Zdenek(dot)Kotala(at)sun(dot)com> wrote:
>
> Yes, because it is not simple write operation. You need to read byte from
> memory to register, set bit and write it back. Write memory itself is atomic
> but somebody could change other bits between read and write.
>
Yeah, but since its just a hint, we can possibly live with some corner
cases. The benefit of avoiding contention on the VM page would easily
out weigh the downside of wrong hints.
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
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