| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: visibility maps |
| Date: | 2008-12-06 14:27:35 |
| Message-ID: | 493A8BD7.6060809@enterprisedb.com |
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| Lists: | pgsql-hackers |
Pavan Deolasee wrote:
> /*
> * We don't need to lock the page, as we're only looking at a single
> bit.
> */
> result = (map[mapByte] & (1 << mapBit)) ? true : false;
>
>
> Isn't this a dangerous assumption to make ? I am not so sure that even a bit
> can be read atomically on all platforms.
Umm, what non-atomic state could the bit be in? Half-set, half-cleared?
Or do you think that if some other bit in proximity is changed, the
other bit would temporarily flip 0->1->0, or something like that? I
don't think that should happen.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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