From: | Gregory Smith <gregsmithpgsql(at)gmail(dot)com> |
---|---|
To: | MauMau <maumau307(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: proposal for 9.5: monitoring lock time for slow queries |
Date: | 2014-10-05 07:57:46 |
Message-ID: | 5430F9FA.5000408@gmail.com |
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Thread: | |
Lists: | pgsql-hackers |
On 8/13/14, 5:14 AM, MauMau wrote:
> I'm interested in b, too. I was thinking of proposing a performance
> diagnostics feature like Oracle's wait events (V$SYSTEM_EVENT and
> V$SESSION_EVENT). So, if you do this, I'd like to contribute to the
> functional design, code and doc review, and testing.
I already wrote up a design like this once:
http://www.postgresql.org/message-id/509300F7.5000803@2ndQuadrant.com
The main problem when I tried to code it was figuring out how to store
the data. When I wrote that, I thought I could just stuff it into a
shared memory block the way pg_stat_statements did. That didn't really
work out. I think it's manageable now because the Dynamic Shared Memory
management written since then has the right sort of shape to do the job.
This is one of those jobs where I think the coding itself is the hard
part, not the design nor the review. What I really want is something
that dumps this data into memory, then a second process that persists to
disk in batches. I think that's the only way we'll get high performance
on reads while still saving enough data to be useful after a crash.
We're working on getting a few things in this area fully funded to dig
into them harder. The idea of designing for high-speed audit logs into
memory and then persisting to disk has a lot of overlap with this one
too, and that may get picked up too.
--
Greg Smith greg(dot)smith(at)crunchydatasolutions(dot)com
Chief PostgreSQL Evangelist - http://crunchydatasolutions.com/
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