On 07/10/2018 08:38 PM, Justin Pryzby wrote:
On Tue, Jul 10, 2018 at 01:54:12PM -0400, Patrick Hemmer wrote:
I'm looking for a way of gathering performance stats in a more usable
way than turning on `log_statement_stats` (or other related modules).
The problem I have with the log_*_stats family of modules is that they
log every single query, which makes them unusable in production. Aside
from consuming space, there's also the problem that the log system
wouldn't be able to keep up with the rate.
There are a couple ideas that pop into mind that would make these stats
more usable:
1. Only log when the statement would otherwise already be logged. Such
as due to the `log_statement` or `log_min_duration_statement` settings.
Did you see: (Added Adrien to Cc);
https://commitfest.postgresql.org/18/1691/
I don't think the existing patch does what you want, but perhaps all that's
needed is this:
if (save_log_statement_stats)
+ if (log_sample_rate==1 || was_logged)
ShowUsage("EXECUTE MESSAGE STATISTICS");
In any case, I'm thinking that your request could/should be considered by
whatever future patch implements sampling (if not implemented/included in the
patch itself).
Hi,
Thanks for Cc, it seems a good idea. Will think about it ;)
If that doesn't do what's needed, that patch might still be a good crash course
in how to start implementing what you need (perhaps on top of that patch).
2. Make stats available in `pg_stat_statements` (or alternate view that
could be joined on). The block stats are already available here, but
others like CPU usage, page faults, and context switches are not.
pg_stat_statements is ./contrib/pg_stat_statements/pg_stat_statements.c which is 3k LOC.
getrusage stuff and log_*_stat stuff is in src/backend/tcop/postgres.c
Justin
