Re: Allow logical replication to copy tables in binary format - Mailing list pgsql-hackers

>       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.
>
> No, logical replication in binary does not fail on apply phase if data types are
> different.
With HEAD, I observe in some case we fail at apply phase because of different data types like
integer vs. bigint as written scenario in [1]. In short, I think we can slightly
adjust your documentation and make it more general so that the description applies to
both table sync phase and apply phase.

I'll suggest a below change for your sentence of logical-replication.sgml.
FROM:
In binary case, it is not allowed to replicate data between different types due to restrictions inherited from COPY.
TO:
Binary format is type specific and does not allow to replicate data between different types according to its
restrictions.

If my idea above is correct, then I feel we can remove all the fixes for create_subscription.sgml.
I'm not sure if I should pursue this perspective of the document improvement
any further after this email, since this isn't essentially because of this patch.

-          Specifies whether the subscription will request the publisher to
-          send the data in binary format (as opposed to text).
+          Specifies whether the subscription will copy the initial data to
+          synchronize relations in binary format and also request the publisher
+          to send the data in binary format too (as opposed to text).

> The concern with upgrade (if data types are not the same) would be not being
> able to create a new subscription with binary enabled or replicate new tables
> added into publication.
> Replication of tables from existing subscriptions would not be affected by this
> change since they will already be in the apply phase, not tablesync.
> Do you think this would still be an issue?
Okay, thanks for explaining this. I understand that
the upgrade concern applies to the table sync that is executed
between text format (before the patch) and binary format (after the patch).