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From: Sami Imseih <[email protected]>
To: Masahiko Sawada <[email protected]>
Cc: Maxim Orlov <[email protected]>
Cc: Postgres hackers <[email protected]>
Subject: Re: POC: Parallel processing of indexes in autovacuum
Date: Fri, 2 May 2025 11:58:30 -0500
Message-ID: <CAA5RZ0vN_RjrHR+HXTkfHydRDZ-yGrpapWQ3-oGj1W34AoftmQ@mail.gmail.com> (raw)
In-Reply-To: <CAD21AoCdx5ZNS_cO7bYz1Zfb+Kw1kuJV2wtewrz7T1pPpjcWGw@mail.gmail.com>
References: <CACG=ezZOrNsuLoETLD1gAswZMuH2nGGq7Ogcc0QOE5hhWaw=cw@mail.gmail.com>
	<CAD21AoCdx5ZNS_cO7bYz1Zfb+Kw1kuJV2wtewrz7T1pPpjcWGw@mail.gmail.com>

Thanks for raising this idea!

I am generally -1 on the idea of autovacuum performing parallel
index vacuum, because I always felt that the parallel option should
be employed in a targeted manner for a specific table. if you have a bunch
of large tables, some more important than others, a/c may end
up using parallel resources on the least important tables and you
will have to adjust a/v settings per table, etc to get the right table
to be parallel index vacuumed by a/v.

Also, with the TIDStore improvements for index cleanup, and the practical
elimination of multi-pass index vacuums, I see this being even less
convincing as something to add to a/v.

Now, If I am going to allocate extra workers to run vacuum in parallel, why
not just provide more autovacuum workers instead so I can get more tables
vacuumed within a span of time?

> Once we have parallel heap vacuum, as discussed in thread[1], it would
> also likely be beneficial to incorporate it into autovacuum during
> aggressive vacuum or failsafe mode.

IIRC, index cleanup is disabled by failsafe.


--
Sami Imseih
Amazon Web Services (AWS)

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