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From: Kyotaro Horiguchi <[email protected]>
To: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Subject: Re: Report oldest xmin source when autovacuum cannot remove tuples
Date: Tue, 02 Jun 2026 16:57:55 +0900 (JST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAOzEurTC+5xuH_X2EBWjW0Fs9iuTq3OMA=1FfT4xx1wYbCAR6g@mail.gmail.com>
References: <[email protected]>
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	<CAOzEurTC+5xuH_X2EBWjW0Fs9iuTq3OMA=1FfT4xx1wYbCAR6g@mail.gmail.com>

Hello.

This may be just my personal preference, but I'd rather see
information about xid horizon retention exposed through a SQL-visible
interface than added to the VACUUM log.

VACUUM VERBOSE already reports the removable cutoff and how old it was
when the operation ended.  That seems sufficient as a signal that the
xid horizon is being held back.

What I would want to investigate after seeing such a signal is not
necessarily what happened to be blocking that particular VACUUM
operation at some earlier point, but what is holding the xid horizon
back now.  For that purpose, a view exposing the current xid/xmin
holders seems more useful and less misleading than adding a
best-effort blocker guess to the VACUUM log.

Also, VACUUM output has traditionally reported facts observed during
the operation.  Since the blocker information is reconstructed
afterwards and is explicitly best-effort, it feels somewhat different
in nature from the rest of the information reported there.

Regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

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