Re: proposal for 9.5: monitoring lock time for slow queries

From: "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com>
> 2014-08-13 13:59 GMT+02:00 MauMau <maumau307(at)gmail(dot)com>:
>> Are you concerned about the impactof collection overhead on the queries
>> diagnosed? Maybe not light, but I'm optimistic. Oracle has the track
>> record of long use, and MySQL provides performance schema starting from
>> 5.6.
>
>
> partially, I afraid about total performance (about impact on IO) - when we
> use a usual tables, then any analyses without indexes are slow, so you
> need
> a indexes, and we cannot deferred index update. You should thinking about
> retention policy - and without partitioning you got massive deletes. So I
> cannot to imagine a usage of table based solution together with some
> higher
> load. Our MVCC storage is not practical for storing only inserted data,
> and
> some custom storage has no indexes - so this design is relative big
> project.
>
> I prefer a possibility to read log via SQL (maybe some FDW) than use
> tables
> for storing log. These tables can be relative very large in few days - and
> we cannot to write specialized engine like MySQL simply.

I didn't mean performance statistics data to be stored in database tables.
I just meant:

* pg_stat_system_events is a view to show data on memory, which returns one
row for each event across the system. This is similar to V$SYSTEM_EVENT in
Oracle.

* pg_stat_session_events is a view to show data on memory, which returns one
row for each event on one session. This is similar to V$SESSION_EVENT in
Oracle.

* The above views represent the current accumulated data like other
pg_stat_xxx views.

* EXPLAIN ANALYZE and auto_explain shows all events for one query. The lock
waits you are trying to record in the server log is one of the events.

Regards
MauMau