RE: Allow logical replication to copy tables in binary format

Hi

Few more minor comments.

On Tuesday, August 16, 2022 2:04 AM Melih Mutlu <m(dot)melihmutlu(at)gmail(dot)com> wrote:
>
>
> My main concern is to break a scenario that was previously working (14
> -> 15) but after a subscriber upgrade
> it won't (14 -> 16).
>
> Fair concern. Some cases that might break the logical replication with version
> upgrade would be:
...
> 3- Copying in binary format would work with the same schemas. Currently,
> logical replication does not require the exact same schemas in publisher and
> subscriber.
> This is an additional restriction that comes with the COPY command.
>
> If a logical replication has been set up with different schemas and subscription
> is created with the binary option, then yes this would break things.
> This restriction can be clearly stated and wouldn't be unexpected though.
>
> I'm also okay with allowing binary copy only for v16 or later, if you think it would
> be safer and no one disagrees with that.
> What are your thoughts?
I agree with the direction to support binary copy for v16 and later.

IIUC, the binary format replication with different data types fails even during apply phase on HEAD.
I thought that means, the upgrade concern only applies to a scenario that the user executes
only initial table synchronizations between the publisher and subscriber
and doesn't replicate any data at apply phase after that. I would say
this isn't a valid scenario and your proposal makes sense.

Best Regards,
Takamichi Osumi