Hi, On Thu, Aug 10, 2023 at 04:30:40PM +0900, Masahiko Sawada wrote: > On Thu, Aug 10, 2023 at 2:27 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > Sawada-San, Julien, and others, do you have any thoughts on the above point? > > IIUC during the old cluster running in the middle of pg_upgrade it > doesn't accept TCP connections. I'm not sure we need to worry about > the case where someone in the same server attempts to create > replication slots during the upgrade.
AFAICS this is only true for non-Windows platform, so we would still need some extra safeguards on Windows. Having those on all platforms will probably be simpler and won't hurt otherwise. > The same is true for other objects, as Amit mentioned. I disagree. As I mentioned before any module registered in shared_preload_libraries can spawn background workers which can perform any activity. There were previous reports of corruption because of multi-xact being generated by such bgworkers during pg_upgrade, I'm pretty sure that there are some modules that create objects (automatic partitioning tools for instance). It's also unclear to me what would happen if some writes are performed by such module at various points of the pg_upgrade process. Couldn't that lead to either data loss or broken slot (as it couldn't stream changes from older major version)?
