On Thu, Oct 11, 2012 at 2:23 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > So where's the race? > > AFAICS it either waits or it doesn't - the code isn't vague on that > point. If we wait we set the flag. > > The point is that lock waits are pretty rare since most locks are > compatible, so triggering a second snap if we waited is not any kind > of problem, even if we waited for a very short time.
That actually wouldn't fix the problem, because we might have this scenario: 1. We take a snapshot. 2. Some other process commits, clearing its XID from its PGPROC and releasing locks. 3. We take a lock. :-( -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
