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
--
http://www.wiesinger.com/
--
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
