Re: DDL support for logical replication

Hi Miles,

One issue is keeping the subscriber and the publisher schema identical.
Running migrations on both the publisher and subscriber does not seem
atomic to me, therefore I don't have a way to enforce consistency between
the two. The use case is simple: schemas change all the time, and keeping
two databases (or more!) in sync manually is tough.

Another issue is migrating large databases (in the terabytes) to a new
version of Postgres with minimal downtime. Say it takes a week or two to
sync up the subscriber with the publisher, we have to enforce a migration
freeze for that duration. That's often inconvenient.

We often want to have a database with a subset of data of a particular
table somewhere else, and logical replication is great, since it allows me
to run write operations on the subscriber. Binary replication forces me to
have two identical databases.

Best,
Lev

On Thu, Oct 10, 2019 at 12:49 PM Miles Elam <miles(dot)elam(at)productops(dot)com>
wrote:

> Hi Lev,
>
> While I don't have an answer to your roadmap question, you've raised a
> different question for me.
>
> What are you expecting to get from logical replication of DDL commands
> that is not served by binary replication? I ask because typically someone
> would want to use logical replication if they wanted triggers to fire on
> the subscriber, they only a subset of all tables replicated, etc.
>
> Perhaps a better question would be "What problem are you trying to solve?"
> rather than focus on how you expected to solve that problem.
>
>
> Cheers,
>
> Miles Elam
>
> On Thu, Oct 10, 2019 at 11:08 AM Lev Kokotov <lev(dot)kokotov(at)gmail(dot)com>
> wrote:
>
>> Hello,
>>
>> Is DDL support on a roadmap for logical replication?
>>
>> Thank you.
>> - Lev
>>
>