Re: optimize file transfer in pg_upgrade

On Wed, Nov 6, 2024 at 04:07:35PM -0600, Nathan Bossart wrote:
> For clusters with many relations, the file transfer step of pg_upgrade can
> take the longest. This step clones, copies, or links the user relation
> files from the older cluster to the new cluster, so the amount of time it
> takes is closely related to the number of relations. However, since v15,
> we've preserved the relfilenodes during pg_upgrade, which means that all of
> these user relation files will have the same name. Therefore, it can be
> much faster to instead move the entire data directory from the old cluster
> to the new cluster and to then swap the catalog relation files.

That is certainly a creative idea. I am surprised the links take so
long. Obviously rollback would be hard, as you mentioned, while now you
can rollback --link until you start. I think it clearly should be
considered. The patch is smaller than I expected.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

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