Re: Notice and share memory corruption

Hannu Krosing <hannu(at)tm(dot)ee> writes:
>> Define your terms more carefully, please. What do you mean by
>> "unable to vacuum" --- what happens *exactly*?

> NOTICE: FlushRelationBuffers(access_right, 2009): block 1944 is
> referenced (private 0, global 2)
> FATAL 1: VACUUM (vc_repair_frag): FlushRelationBuffers returned -2

Oh, that's interesting. This error indicates that some prior
transaction neglected to release a reference count on a shared buffer.
We have seen sporadic reports of this problem in 7.0, but so far no
one has come up with a reproducible example. If you can boil down
your script to something that reproducibly causes the problem then
that'd be a great help in tracking it down.

If you have clients that sometimes disconnect in the middle of a
transaction, it might help to apply the attached patch.

> Maybe i have to really restart it (instead of doing
> /etc/rc.d/init.d/postgresql restart)
> by running killall -9 /usr/bin/postgres

Restarting the postmaster should clear the problem (by releasing and
reinitializing shared memory). I dunno where you got the idea that
kill -9 was a recommended way of shutting down the system, but I sure
wouldn't recommend it. A plain kill on the postmaster ought to do it
(see the pg_ctl script in release 7.0.*).

regards, tom lane

*** src/backend/tcop/postgres.c.orig Sat May 20 22:23:30 2000
--- src/backend/tcop/postgres.c Wed Aug 30 16:47:51 2000
***************
*** 1459,1465 ****
* Initialize the deferred trigger manager
*/
if (DeferredTriggerInit() != 0)
! proc_exit(0);

SetProcessingMode(NormalProcessing);

--- 1459,1465 ----
* Initialize the deferred trigger manager
*/
if (DeferredTriggerInit() != 0)
! goto normalexit;

SetProcessingMode(NormalProcessing);

***************
*** 1479,1490 ****
TPRINTF(TRACE_VERBOSE, "AbortCurrentTransaction");

AbortCurrentTransaction();
! InError = false;
if (ExitAfterAbort)
! {
! ProcReleaseLocks(); /* Just to be sure... */
! proc_exit(0);
! }
}

Warn_restart_ready = true; /* we can now handle elog(ERROR) */
--- 1479,1489 ----
TPRINTF(TRACE_VERBOSE, "AbortCurrentTransaction");

AbortCurrentTransaction();
!
if (ExitAfterAbort)
! goto errorexit;
!
! InError = false;
}

Warn_restart_ready = true; /* we can now handle elog(ERROR) */
***************
*** 1553,1560 ****
if (HandleFunctionRequest() == EOF)
{
/* lost frontend connection during F message input */
! pq_close();
! proc_exit(0);
}
break;

--- 1552,1558 ----
if (HandleFunctionRequest() == EOF)
{
/* lost frontend connection during F message input */
! goto normalexit;
}
break;

***************
*** 1608,1618 ****
*/
case 'X':
case EOF:
! if (!IsUnderPostmaster)
! ShutdownXLOG();
! pq_close();
! proc_exit(0);
! break;

default:
elog(ERROR, "unknown frontend message was received");
--- 1606,1612 ----
*/
case 'X':
case EOF:
! goto normalexit;

default:
elog(ERROR, "unknown frontend message was received");
***************
*** 1642,1651 ****
if (IsUnderPostmaster)
NullCommand(Remote);
}
! } /* infinite for-loop */

! proc_exit(0); /* shouldn't get here... */
! return 1;
}

#ifndef HAVE_GETRUSAGE
--- 1636,1655 ----
if (IsUnderPostmaster)
NullCommand(Remote);
}
! } /* end of main loop */
!
! normalexit:
! ExitAfterAbort = true; /* ensure we will exit if elog during abort */
! AbortOutOfAnyTransaction();
! if (!IsUnderPostmaster)
! ShutdownXLOG();
!
! errorexit:
! pq_close();
! ProcReleaseLocks(); /* Just to be sure... */
! proc_exit(0);

! return 1; /* keep compiler quiet */
}

#ifndef HAVE_GETRUSAGE