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help / color / mirror / Atom feedFrom: Andrei Zubkov <[email protected]>
To: Masahiko Sawada <[email protected]>
To: Alena Rybakina <[email protected]>
Cc: jian he <[email protected]>
Cc: Alexander Korotkov <[email protected]>
Cc: Ilia Evdokimov <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: [email protected]
Subject: Re: Vacuum statistics
Date: Fri, 27 Sep 2024 22:25:14 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAD21AoAVK7DwTZLfhwuRhTGgR=_ASu5YshEg_Cmpojk5ZdZ3tA@mail.gmail.com>
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Hi,
On Fri, 2024-09-27 at 11:15 -0700, Masahiko Sawada wrote:
> I'm concerned that a pg_stat_vacuum_tables view has some duplicated
> statistics that we already collect in different ways. For instance,
> total_blks_{read,hit,dirtied,written} are already tracked at
> system-level by pg_stat_io,
pg_stat_vacuum_tables.total_blks_{read,hit,dirtied,written} tracks
blocks used by vacuum in different ways while vacuuming this particular
table while pg_stat_io tracks blocks used by vacuum on the cluster
level.
> and per-relation block I/O statistics can
> be collected using pg_stat_statements.
This is impossible. pg_stat_statements tracks block statistics on a
statement level. One statement could touch many tables and many
indexes, and all used database blocks will be counted by the
pg_stat_statements counters on a statement-level. Autovacuum statistics
won't be accounted by the pg_stat_statements. After all,
pg_stat_statements won't hold the statements statistics forever. Under
pressure of new statements the statement eviction can happen and
statistics will be lost.
All of the above is addressed by relation-level vacuum statistics held
in the Cumulative Statistics System proposed by this patch.
--
regards, Andrei Zubkov
Postgres Professional
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