Re: Fix bug in multixact Oldest*MXactId initialization and access

[Chao Li]

> On Mar 2, 2026, at 10:34, Sami Imseih <samims...@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/