On 2011-05-10 14:48, Robert Haas wrote:
> We could avoid all of this complexity - and the possibility of pinning
> the visibility map page needlessly - by locking the heap buffer first
> and then pinning the visibility map page if the heap page is
> all-visible. However, that would involve holding the lock on the heap
> buffer across a possible disk I/O to bring the visibility map page
> into memory, which is something the existing code tries pretty hard to
> avoid.
Assuming that the visibillity map would be used for visibillity testing,
just picking the lock would effectively mean "we want it in the buffers",
which would not be that bad?
Or what is the downside for keeping it across IO? Will it block other
processes trying to read it?
--
Jesper