Re: RFC: Timing Events

> I don't see all that going into core without a much bigger push than I
> think people will buy. What people really want for all these is a
> proper trending system, and that means graphs and dashboards and
> bling--not a history table.

Well, I'm particularly thinking for autoconfiguration. For example, to
set vacuum_freeze_min_age properly, you have to know the XID "burn rate"
of the server, which is only available via history. I really don't want
to be depending on a graphical monitoring utility to find these things out.

> This whole approach has the assumption that things are going to fall off
> sometimes. To expand on that theme for a second, right now I'm more
> worried about the "99%" class of problems. Neither pg_stat_statements
> nor this idea are very good for tracking the rare rogue problem down.
> They're both aimed to make things that happen a lot more statistically
> likely to be seen, by giving an easier UI to glare at them frequently.
> That's not ideal, but I suspect really fleshing the whole queue consumer
> -> table idea needs to happen to do much better.

I'm just concerned that for some types of incidents, it would be much
more than 1% *of what you want to look at* which fall off. For example,
consider a server which does 95% reads at a very high rate, but has 2%
of its writes cronically having lock waits. That's something you want
to solve, but it seems fairly probably that these relatively infrequent
queries would have fallen off the bottom of pg_stat_statements. Same
thing with the relative handful of queries which do large on-disk sorts.

The problem I'm worried about is that pg_stat_statements is designed to
keep the most frequent queries, but sometimes the thing you really need
to look at is not in the list of most frequent queries.

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com