Re: visibility maps

On Thu, Dec 11, 2008 at 7:15 PM, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
>
>
> Yeah, if we accept that bits can be bogusly set. There is scenarios where
> that can happen already, but they involve crashing, not during normal
> operation and clean shut down. In the future, I'd like to move in the
> direction of making the visibility map *more* reliable, not less, ultimately
> allowing index-only-scans, so I'd rather not start relaxing that.
>

Do we have any tests to prove that the VM page lock does not indeed
become a bottleneck ? I can do some if we don't have already.

> Only the first update to a page needs to clear the bit in the visibility
> map, so I don't think it'll become a bottleneck in practice. Frequently
> updated pages will never have the bit set in the visibility map to begin
> with.
>

Well that's true only if you reject my heap-prune patch :-) Otherwise,
heap-prune will again set the bit (and I believe that's the right
thing to do)

Thanks,
Pavan



-- 
Pavan Deolasee
EnterpriseDB     http://www.enterprisedb.com