> > Changing the default opclasses should work if we make
> > pg_dump --binary-upgrade dump the default opclasses with indexes
> > and exclusion constraints. I think it makes sense to do so in
> > --binary-upgrade mode. I can try to come with a patch for this.
>
> Can you explain it a bit more detail? I didn't get it.
pg_upgrade uses pg_dump --binary-upgrade to dump the schema of
the old database. Now, it generates CREATE INDEX statements without
explicit opclass if opclass is the default. We can change pg_dump
to generate the statements with opclass even if opclass is the default
in --binary-upgrade mode.