Re: two shared memory segments?

Ed Loehr <ed@loehrtech.com> writes:
> On Wednesday December 21 2005 8:24 pm, Tom Lane wrote:
>> I'd say that you had a backend crash, causing the postmaster
>> to abandon the original shared memory segment and make a new
>> one, but the old segment is still attached to by a couple of
>> processes.

> Does that make sense even if the creating pid is the same for
> both?

Sure.  The postmaster survives backend crashes --- that's the point
of having a separate postmaster process at all.

>> There was a bug awhile back whereby the stats support
>> processes failed to detach from shared memory and thus would
>> cause a dead shmem segment to hang around like this.  What PG
>> version are you running?

> This is an old 7.3.7 cluster.

[ digs in CVS logs... ]  Hmm.  AFAICT that bug was fixed in 7.3.5:

2003-11-30 16:56  tgl

    * src/: backend/port/sysv_shmem.c, backend/postmaster/pgstat.c,
    include/storage/pg_shmem.h (REL7_3_STABLE): Back-patch fix to cause
    stats processes to detach from shared memory, so that they do not
    prevent the postmaster from deleting the shmem segment during crash
    recovery.

You sure it's a 7.3.7 postmaster?  Can you dig down to determine exactly
which processes are attached to the older shmem segment?

            regards, tom lane