Scott Marlowe <scott.marlowe@xxxxxxxxx> writes: > On Mon, Jul 20, 2009 at 4:44 PM, David Kerr<dmk@xxxxxxxxxxxxxx> wrote: >> I'm playing around with different options for a median function. this one got out of hand >> and was taking too long, so i wanted to kill it: >> >> test=# select array_median(array(select t1 from test2 order by 1)); >> ^CCancel request sent >> >> It just sits there, it's been trying to die for 1/2 an hour. > What's most likely happening is that it's stuck in a tight loop that > doesn't check for interrupts, so it just keeps on going. Yeah, that was my first thought. What is array_median()? If it's custom C code, you probably forgot to put CHECK_FOR_INTERRUPTS in suitable place(s). > You can kill -9 a process. It'll cause the postmaster to kill all > backends and flush the buffers if I remember correctly. Yeah, not the > ideal solution in production but on a non-prod machine it's an ok way > to get out of these issues. And even in production, it's often much > faster to kill -9 a single process than to wait for it to finish. I > think there might be choices other than -9 here, but I can't recall > them off the top of my head. Kill -9 on the postmaster is disrecommended for a number of reasons, but kill -9 on an individual backend is quite predictable. What it will do is cause *all* of your open sessions to get aborted. If you can tolerate that then do it. If you can't tolerate that, you can try a SIGTERM, but I suspect that if the thing is too hosed to notice a cancel (a/k/a SIGINT) then it won't notice SIGTERM either. SIGTERM on a single backend isn't as safe as the other options anyhow. There used to be bugs in that code path (still ARE known bugs, if you're not running a pretty recent PG release) and I wouldn't trust it totally. One thing you should definitely not try is SIGQUIT. That will kill the process all right (unless it's wedged a lot worse than I think) but it will not do anything about cleaning up its shared memory state, and that almost certainly will cause problems later. Better to find a time when it's okay to use SIGKILL. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
