Re: vacuum issues under load?

Ben Chobot <bench@silentmedia.com> writes:
> We have recently discovered a problem with our slony-1 cluster of 8.1.19
> installs. Specifically, we are unable to vacuum a table on the master
> node; vacuum always hangs on the same index of the same table. If we do a
> slony switchover and make the other node the master, then *it* will become
> unable to vacuum that index. Vacuum on the slave always works quickly and
> without issue. Vacuum does not hang anywhere else.

> When we tried to strace the vacuuming backend, it appeared as if it was
> trying to acquire a lock, but pg_lock showed nothing unexpected for that
> index.

Try attaching to the process with gdb and getting a stack trace.

Also ask on the slony lists if anyone's seen anything like this.  I
don't know a reason for slony to have any effect like that, but there's
got to be *something* weird going on.

            regards, tom lane