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From: Chao Li <li.evan.chao@gmail.com>
To: Sami Imseih <samimseih@gmail.com>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Yura Sokolov <y.sokolov@postgrespro.ru>
Cc: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
Subject: Re: Fix bug in multixact Oldest*MXactId initialization and access
Date: Mon, 2 Mar 2026 12:08:02 +0800
Message-ID: <A0249625-0EF4-4068-854F-0592139DFBC1@gmail.com> (raw)
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> On Mar 2, 2026, at 10:34, Sami Imseih <samimseih@gmail.com> wrote:
> 
>> New version attached.
> 
> The comment here:
> 
> +static inline MultiXactId *
> +PreparedXactOldestMemberMXactIdSlot(ProcNumber procno)
> +{
> +       /*
> +        * The entries with indexes >= MaxBackends in the OldestMemberMXactId
> +        * array are reserved for regular backends.
> 
> should say "array are reserved for prepared transactions"
> 

+1

And I saw the other code comment in multixact.c around line 162 needs an update because of this patch:
```
* Per-backend data starts here. We have two arrays stored in the area
* immediately following the MultiXactStateData struct. Each is indexed by
* ProcNumber.
```

It says “Each is indexed by ProcNumber”, but it’s no longer accurate for OldestMemberMXactId prepared-xact entries, which now use index (procno - FIRST_PREPARED_XACT_PROC_NUMBER).

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/









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