Adam Witney <awitney(at)sghms(dot)ac(dot)uk> writes:
> I am logged in as the superuser, and I just switched stats_command_string
> on.
Just now? Too late then --- it needed to be on at the time the other
guy started his query, else he did not send the string to the stats
collector.
> I did find a reference on google to the fact that there was/is a max query
> size length for this?
Yeah, but it truncates, it doesn't just drop the string.
If you are feeling desperate you can attach to the other backend with
gdb:
$ gdb /path/to/postgres backend-PID
gdb> print debug_query_string
gdb> quit
detach and let process continue? y
$
regards, tom lane