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From: Heikki Linnakangas <[email protected]>
To: Maxim Orlov <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Alexander Korotkov <[email protected]>
Cc: wenhui qiu <[email protected]>
Cc: Postgres hackers <[email protected]>
Cc: Ashutosh Bapat <[email protected]>
Subject: Re: POC: make mxidoff 64 bits
Date: Tue, 25 Nov 2025 12:07:27 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CACG=ezaWg7_nt-8ey4aKv2w9LcuLthHknwCawmBgEeTnJrJTcw@mail.gmail.com>
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Looking at the upgrade code, in light of the "IPC/MultixactCreation on 
the Standby server" thread [1], I think we need to make it more 
tolerant. It's possible that there are 0 offsets in 
pg_multixact/offsets. That might or might not be a problem: it's OK as 
long as those multixids don't appear in any heap table, or you might 
actually have lost those multixids, which is bad but the damage has 
already been done and upgrade should not get stuck on it. 
GetOldMultiXactIdSingleMember() currently asserts that the offset is 
never zero, but it should try to do something sensible in that case 
instead of just failing.

[1] 
https://www.postgresql.org/message-id/172e5723-d65f-4eec-b512-14beacb326ce%40yandex.ru

- Heikki






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