Re: Allow non-superuser to cancel superuser tasks.

On Wed, Jul 10, 2024 at 02:14:55PM +0900, Michael Paquier wrote:
> +# Only non-superuser roles granted pg_signal_autovacuum_worker are allowed
> +# to signal autovacuum workers.  This test uses an injection point located
> +# at the beginning of the autovacuum worker startup.

nitpick: Superuser roles are also allowed to signal autovacuum workers.
Maybe this should read "Only roles with privileges of..."

> +# Create some content and set an aggressive autovacuum.
> +$node->safe_psql(
> +	'postgres', qq(
> +    CREATE TABLE tab_int(i int);
> +    ALTER TABLE tab_int SET (autovacuum_vacuum_cost_limit = 1);
> +    ALTER TABLE tab_int SET (autovacuum_vacuum_cost_delay = 100);
> +));
> +
> +$node->safe_psql(
> +	'postgres', qq(
> +    INSERT INTO tab_int VALUES(1);
> +));
> +
> +# Wait until an autovacuum worker starts.
> +$node->wait_for_event('autovacuum worker', 'autovacuum-worker-start');

I'm not following how this is guaranteed to trigger an autovacuum quickly.
Shouldn't we set autovacuum_vacuum_insert_threshold to 1 so that it is
eligible for autovacuum?

> +# Wait for the autovacuum worker to exit before scanning the logs.
> +$node->poll_query_until('postgres',
> +	"SELECT count(*) = 0 FROM pg_stat_activity "
> +	. "WHERE pid = $av_pid AND backend_type = 'autovacuum worker';");

WFM.  Even if the PID is quickly reused, this should work.  We just might
end up waiting a little longer.

Is it worth testing cancellation, too?

-- 
nathan