Re: visibility maps

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