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From: Andrei Zubkov <[email protected]>
To: Alena Rybakina <[email protected]>
To: PostgreSQL Developers <[email protected]>
To: Andrey Lepikhov <[email protected]>
Subject: Re: Vacuum statistics
Date: Thu, 30 May 2024 22:19:26 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Hi,

Th, 30/05/2024 at 10:33 -0700, Alena Rybakina wrote:
> I suggest gathering information about vacuum resource consumption for
> processing indexes and tables and storing it in the table and index 
> relationships (for example, PgStat_StatTabEntry structure like it has
> realized for usual statistics). It will allow us to determine how
> well 
> the vacuum is configured and evaluate the effect of overhead on the 
> system at the strategic level, the vacuum has gathered this
> information 
> already, but this valuable information doesn't store it.
> 
It seems a little bit unclear to me, so let me explain a little the
point of a proposition.

As the vacuum process is a backend it has a workload instrumentation.
We have all the basic counters available such as a number of blocks
read, hit and written, time spent on I/O, WAL stats and so on.. Also,
we can easily get some statistics specific to vacuum activity i.e.
number of tuples removed, number of blocks removed, number of VM marks
set and, of course the most important metric - time spent on vacuum
operation.

All those statistics must be stored by the Cumulative Statistics System
on per-relation basis. I mean individual cumulative counters for every
table and every index in the database.

Such counters will provide us a clear view about vacuum workload on
individual objects of the database, providing means to measure the
efficiency of performed vacuum fine tuning.
-- 
Andrei Zubkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

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