Re: [Proposal] Add accumulated statistics for wait event

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Phil Florent <philflorent(at)hotmail(dot)com>
Cc: "Yotsunaga, Naoki" <yotsunaga(dot)naoki(at)jp(dot)fujitsu(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: [Proposal] Add accumulated statistics for wait event
Date: 2018-10-04 10:58:41
Message-ID: 20181004105841.GD1256@paquier.xyz
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On Thu, Oct 04, 2018 at 09:32:37AM +0000, Phil Florent wrote:
> I am a DB beginner, so please tell me. It says that you can find
> events that are bottlenecks in sampling, but as you saw above, you can
> not find events shorter than the sampling interval, right?

Yes, which is why it would be as simple as making the interval shorter,
still not too short so as it bloats the amount of information fetched
which needs to be stored and afterwards (perhaps) treated for analysis.
This gets rather close to signal processing. A simple image is for
example, assuming that event A happens 100 times in an interval of 1s,
and event B only once in the same interval of 1s, then if the snapshot
interval is only 1s, then in the worst case A would be treated an equal
of B, which would be wrong.
--
Michael

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