Re: Making pg_rewind faster

Hey Srinath

On Thu, Oct 9, 2025 at 12:09 PM Srinath Reddy Sadipiralla
<srinath2133@gmail.com> wrote:
> ...
> 1) if the timeline switch happens in middle of segment ,copy data from the last WAL segment and create WAL file with
samesegno but different timelineID,in this case the starting WAL file for the new timeline will be
000000020000000000000003
> 2) if the timeline switch happens at segment boundary , just create next segment for this case the starting WAL file
forthe new timeline will be 000000020000000000000004 
>
> so basically the files which exists in source and not in target like the new timeline WAL segments will be copied to
targetin total before we reach decide_wal_file_action , so i think we don't need to think about copying WAL files after
divergencepoint by calculating and checking against last_common_segno which we are doing in our current approach , i
thinkwe can just do 
>
> ...

That's a great point. I need to think about it some more but the
reasoning makes sense to me.
I think 'last_common_segno ' is only useful as another sanity check
but we already have the size
ones.

Thanks,

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John Hsu - Amazon Web Services