Re: use CREATE DATABASE STRATEGY = FILE_COPY in pg_upgrade

On Fri, Jun 14, 2024 at 5:29 PM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
> On Wed, Jun 12, 2024 at 09:41:01AM -0500, Nathan Bossart wrote:
> > Actually, I think you are right that we need a manual checkpoint, except I
> > think we need it to be after prepare_new_globals(). set_frozenxids()
> > connects to each database (including template0) and updates a bunch of
> > pg_class rows, and we probably want those on disk before we start copying
> > the files to create all the user's databases.
>
> Here is an updated patch.

OK, I have a (probably) stupid question. The comment says:

+ * In binary upgrade mode, we can skip this checkpoint because neither of
+ * these problems applies: we don't ever replay the WAL generated during
+ * pg_upgrade, and we don't concurrently modify template0 (not to mention
+ * that trying to take a backup during pg_upgrade is pointless).

But what happens if the system crashes during pg_upgrade? Does this
patch make things worse than they are today? And should we care?

--
Robert Haas
EDB: http://www.enterprisedb.com