Excerpts from Bruce Momjian's message of mar mar 13 14:00:52 -0300 2012: > > On Tue, Mar 06, 2012 at 04:39:32PM -0300, Alvaro Herrera wrote:
> > When there is a single locker in a tuple, we can just store the locking info > > in the tuple itself. We do this by storing the locker's Xid in XMAX, and > > setting hint bits specifying the locking strength. There is one exception > > here: since hint bit space is limited, we do not provide a separate hint bit > > for SELECT FOR SHARE, so we have to use the extended info in a MultiXact in > > that case. (The other cases, SELECT FOR UPDATE and SELECT FOR KEY SHARE, > > are > > presumably more commonly used due to being the standards-mandated locking > > mechanism, or heavily used by the RI code, so we want to provide fast paths > > for those.) > > Are those tuple bits actually "hint" bits? They seem quite a bit more > powerful than a "hint". I'm not sure what's your point. We've had a "hint" bit for SELECT FOR UPDATE for ages. Even 8.2 had HEAP_XMAX_EXCL_LOCK and HEAP_XMAX_SHARED_LOCK. Maybe they are misnamed and aren't really "hints", but it's not the job of this patch to fix that problem. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
