On Thu, Dec 9, 2021 at 5:12 PM Bossart, Nathan <bossa...@amazon.com> wrote: > As Andres noted, such a feature might be useful during normal > operation, too. Perhaps the vacuumdb --min-xid-age stuff should be > moved to a new VACUUM option.
I was thinking of something like pg_import_system_collations() for this: a function that's built-in, and can be called in single user mode, that nevertheless doesn't make any assumptions about how it may be called. Nothing stops a superuser from calling pg_import_system_collations() themselves, outside of initdb. That isn't particularly common, but it works in the way you'd expect it to work. It's easy to test. I imagine that this new function (to handle maintenance tasks in the event of a wraparound emergency) would output information about its progress. For example, it would make an up-front decision about which tables needed to be vacuumed in order for the current DB's datfrozenxid to be sufficiently new, before it started anything (with handling for edge-cases with many tables, perhaps). It might also show the size of each table, and show another line for each table that has been processed so far, as a rudimentary progress indicator. We could still have a separate option for the postgres executable, just to invoke single-user mode and call this function. It would mostly just be window dressing, of course, but that still seems useful. -- Peter Geoghegan
