OK, it looks like my problem was just the postgres server having a bad
day, I just looked in the logfile and found this right after the
LockAcquire errors:
DEBUG: all server processes terminated; reinitializing shared memory
and semaphores
DEBUG: database system was interrupted at 2003-02-25 16:32:14 PST
DEBUG: checkpoint record is at 10/10C3F26C
DEBUG: redo record is at 10/10C3F26C; undo record is at 0/0; shutdown
FALSE
DEBUG: next transaction id: 686501; next oid: 85358132
DEBUG: database system was not properly shut down; automatic recovery
in progress
DEBUG: ReadRecord: record with zero length at 10/10C3F2AC
DEBUG: redo is not required
FATAL 1: The database system is starting up
DEBUG: database system is ready
and now I can't get the LockAcquire errors to happen again at all.
Looks like it was just a passing gremlin, hopefully it won't come back
to visit too often.
Sorry for the noise on the list!
Bob
Begin forwarded message:
> From: Bob Smith <bsmith@h-e.com>
> Date: Tue Feb 25, 2003 16:55:57 US/Pacific
> To: pgsql-sql <pgsql-sql@postgresql.org>
> Subject: Postgres locking
>
>
> I'm trying to use select for update locks in Postgres. When I do this:
>
> begin work;
> select data from table where key = 1 for update;
>
> in two psql's running simultaneously, about half the time the second
> transaction blocks and waits for the first to end (which is what I
> want it to do), the other half the time I get this:
>
> ERROR: XactLockTableWait: LockAcquire failed
>
> and the transaction is aborted. I can't find any pattern, if I do the
> same statements in the same order several times, it will be block one
> time and error the next apparently at random. I also tried using LOCK
> TABLE and found the same basic problem, sometimes the second
> transaction will block, other times it will abort with:
>
> ERROR: LockRelation: LockAcquire failed
>
> Do I have a configuration problem? Is this a bug in Postgres? I'm
> still running 7.2.1, would upgrading to 7.3 fix this?
>
> Thanks!
>
> Bob Smith
> Hammett & Edison, Inc.
> bsmith@h-e.com
>
>
