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

2014-08-13 15:22 GMT+02:00 MauMau <maumau307(at)gmail(dot)com>:

> 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.
>

I am little bit sceptic about only memory based structure. Is it this
concept acceptable for commiters?

Pavel

>
> Regards
> MauMau
>
>