On Apr 11, 2011, at 6:06 PM, Robert Haas wrote: > On Sun, Apr 10, 2011 at 5:03 PM, A.M. <age...@themactionfaction.com> wrote: >> To ensure that no two postmasters can startup in the same data directory, I >> use fcntl range locking on the data directory lock file, which also works >> properly on (properly configured) NFS volumes. Whenever a postmaster or >> postmaster child starts, it acquires a read (non-exclusive) lock on the data >> directory's lock file. When a new postmaster starts, it queries if anything >> would block a write (exclusive) lock on the lock file which returns a >> lock-holding PID in the case when other postgresql processes are running. > > This seems a lot leakier than what we do now (imagine, for example, > shared storage) and I'm not sure what the advantage is. I was > imagining keeping some portion of the data in sysv shm, and moving the > big stuff to a POSIX shm that would operate alongside it.
What do you mean by "leakier"? The goal here is to extinguish SysV shared memory for portability and convenience benefits. The mini-SysV proposal was implemented and shot down by Tom Lane. Cheers, M -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers