Re: Periodic freezing of backend processes

Andrew McMillan <Andrew@catalyst.net.nz> writes:
> I am finding that I periodically have a backend process just 'freeze' on
> me.

Needs to be looked at, for sure.

> What can I do to tickle the backend processes to get it to tell me where
> it is at?

What I'd do is attach to it with gdb and poke around.

    gdb path-of-postgres-executable
    attach PID-of-target-process
    bt
    ...

It helps if you've compiled the backend with -g.  It might also be
useful to enable Asserts.

> I have found that if I kill the backend process that is locked up, then
> do exactly the same query, it locks up again.  BUT if I shut down and
> restart the postmaster and then do exactly the same query (reload my web
> page, in fact) the response is immediate again.

Sounds like the problem is associated with some particular configuration
of shared memory.  Perhaps some prior query has failed to release a
lock, or some such?

            regards, tom lane