Re: database vacuum from cron hanging

I wrote:
> "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
>> (gdb) p BufferDescriptors[781]
>> $1 = {tag = {rnode = {spcNode = 1663, dbNode = 16385, relNode = 2666}, blockNum = 1}, flags = 70, usage_count = 5, refcount = 4294967294,
>> wait_backend_pid = 748, buf_hdr_lock = 0 '\0', buf_id = 781, freeNext = -2, io_in_progress_lock = 1615, content_lock = 1616}

> Whoa. refcount -2?

BTW, at this point your most helpful move would be to rebuild with
--enable-cassert (keeping --enable-debug) and go back to your current
test mix. The only place that decrements refcount has
Assert(refcount > 0), so it seems quite likely that you'll soon see
an assertion crash, and then getting a stack trace from that would
probably expose the culprit immediately. (Make sure you are running
the postmaster under ulimit -c unlimited so that you will get a core
dump file to trace...)

regards, tom lane