Re: file cloning in pg_upgrade and CREATE DATABASE

On 10/10/2018 21:50, Bruce Momjian wrote:
>> I see. Peter is proposing to have a fourth mode, essentially
>> --transfer-mode=clone-or-copy.
>
> Uh, if you use --link, and the two data directories are on different
> file systems, it fails. No one has ever asked for link-or-copy, so why
> are we considering clone-or-copy? Are we going to need
> link-or-clone-or-copy too? I do realize that clone and copy have
> non-destructive behavior on the old cluster once started, so it does
> make some sense to merge them, unlike link.

I'm OK to get rid of the clone-or-copy mode. I can see the confusion.

The original reason for this behavior was that the Linux implementation
used copy_file_range(), which does clone-or-copy without any way to
control it. But the latest patch doesn't use that anymore, so we don't
really need it, if it's controversial.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services