Re: PostgreSQL strugling during high load

> >>The "vacuum cost" parameters can be adjusted to make vacuums fired
> >>by pg_autovacuum less of a burden. I haven't got any specific numbers
> >>to suggest, but perhaps someone else does.
> >
> > It looks like that not only vacuum causes our problems. vacuum_cost
> > seems to lower vacuum impact but we are still noticing slow queries
"storm".
> > We are logging queries that takes >2000ms to process.
> > And there is quiet periods and then suddenly 30+ slow queries appears
in
> > log within the same second. What else could cause such behaviour?
>
> I've seen that happen when you're placing (explicitly or
> *implicitly*) locks on the records you're trying to update/delete.
>
> If you're willing to investigate, `pg_locks' system view holds
> information about db locks.

Hm. Yes. Number of locks varies quite alot (10-600). Now what to
investigate
further? We do not use explicit locks in our functions. We use quite simple
update/delete where key=something;
Some sample (select * from pg_locks order by pid) is below.

Thanks,

Mindaugas

| | 584302172 | 11836 | ExclusiveLock | t
17236 | 17230 | | 11836 | AccessShareLock | t
17236 | 17230 | | 11836 | RowExclusiveLock | t
127103 | 17230 | | 11836 | RowExclusiveLock | t
127106 | 17230 | | 11836 | RowExclusiveLock | t
127109 | 17230 | | 11836 | AccessShareLock | t
127109 | 17230 | | 11836 | RowExclusiveLock | t
127109 | 17230 | | 11837 | AccessShareLock | t
127109 | 17230 | | 11837 | RowExclusiveLock | t
17236 | 17230 | | 11837 | AccessShareLock | t
17236 | 17230 | | 11837 | RowExclusiveLock | t
127106 | 17230 | | 11837 | RowExclusiveLock | t
127103 | 17230 | | 11837 | RowExclusiveLock | t
| | 584302173 | 11837 | ExclusiveLock | t
127103 | 17230 | | 11838 | RowExclusiveLock | t
17236 | 17230 | | 11838 | RowExclusiveLock | t
127109 | 17230 | | 11838 | RowExclusiveLock | t
| | 584302174 | 11838 | ExclusiveLock | t
17285 | 17230 | | 11838 | AccessShareLock | t
17251 | 17230 | | 11838 | AccessShareLock | t
130516 | 17230 | | 11838 | AccessShareLock | t
127106 | 17230 | | 11838 | RowExclusiveLock | t
17278 | 17230 | | 11838 | AccessShareLock | t