On 12/19/11 10:04 AM, Mario Splivalo wrote:
I need to have postgres role to be able to cancel queries run by that
same role.

I know that I can kill the client connection that started the query, but
I also need to have that role connect to postgres and kill some of it's
running queries.

It's on postgres 9.1.1, running on Debian Squeeze.

One idea that comes to mind is to have a special user account on the box
which would have sudo privileges to the script which will issue 'sh
postgres -c 'psql -c "select pg_cancel_backend(<pid>)"', but before that
run checks that<pid>  is actually owned by correct role, etc, etc. But,
all that seems very fishy.

Has anyone had similar requests, and maybe solved them somehow?
Yes.

First of all, you really don't want to do this.  If there's any other way, find 
it.

In our case, we use a third-party library that sometimes gets stuck on problems 
that would take a virtually infinite time to solve, and for reasons having to 
do with NP-complete theory, you can't easily detect them ahead of time.  So....

Backend Postgres processes run as the Postgres user, so they have permission to 
kill each other.  You write an add-on function that just kills a process:

  select my_kill_backend(pid);

Naturally, this is very dangerous. There are all sorts of security 
implications.  You want to use signal 2 or 15, not 9.  And so forth.

Craig

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