Re: pg_basebackup, manifests and backends older than ~12

Hi,

On 2020-04-10 16:32:08 -0400, David Steele wrote:
> On 4/10/20 4:09 AM, Michael Paquier wrote:
> >
> > I have noticed that attempting to use pg_basebackup from HEAD leads to
> > failures when using it with backend versions from 12 and older:
> > $ pg_basebackup -D hoge
> > pg_basebackup: error: backup manifests are not supported by server
> > version 12beta2
> > pg_basebackup: removing data directory "hoge"
> >
> > This is a bit backwards with what we did in the past to maintain
> > compatibility silently when possible, for example look at the handling
> > of temporary replication slots. Instead of an error when means to
> > force users to have to specify --no-manifest in this case, shouldn't
> > we silently disable the generation of the backup manifest? We know
> > that this option won't work on older server versions anyway.
>
> I'm a bit conflicted here. I see where you are coming from, but given that
> writing a manifest is now the default I'm not sure silently skipping it is
> ideal.

I think we at the very least should add a hint about how to perform a
backup without a manifest.

Greetings,

Andres Freund