Re: PG 8.3 and large shared buffer settings

On Sat, 26 Sep 2009, Greg Smith wrote:

> On Fri, 25 Sep 2009, Jeff Janes wrote:
>
>> Does it do this even if the block was already in shared_buffers?
>
> Usually not.  The buffer ring algorithm is used to manage pages that are read
> in specifically to satisfy a sequential scan (there's a slightly different
> ring method used for VACUUM too).  If the buffer you need is already
> available and not "pinned" (locked by someone else), it's not read from disk
> again.  Instead, its usage count is incremently only if it's at zero (this
> doesn't count as a use unless it's about to be evicted as unused), and it's
> returned without being added to the ring.
>

Hello Greg,

What happens when a postmaster dies (e.g. core dump, kill -9, etc.). How
is reference counting cleaned up and the lock removed?

Thnx.

Ciao,
Gerhard

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