Re: Feature Request - DDL deployment with logical replication

On Fri, Mar 30, 2018 at 2:26 AM, Konstantin Knizhnik <
k(dot)knizhnik(at)postgrespro(dot)ru> wrote:

>
> Our team in PostgresPro is also very interested in this discussion,
> because we are using logical decoding in multimaster.
> Right now in multimaster DDLs are replicated in this same way as in
> pglogical, using "logical messages" with correspondent DDL statements.
> There are a couple of problems related with this approach, for example mix
> of DDL with DML (create table as...) which we have addressed in multimaster.
>

IMO, I wouldn't even allow CREATE TABLE AS especially as an initial
feature. In our environment, I have rarely if even seen an application
migration that uses CREATE TABLE AS, and it's an acceptable compromise for
us to simply disallow it. The way I have written pgl_ddl_deploy is to
disallow CREATE TABLE AS from being replicated. IMO that's a very small
price to pay.

My whole point is that in most architectures, DBAs decide to deploy the
same SQL on providers and subscribers. Yes it isn't perfect, but IMO, it
is very helpful to try to automate that idea, as opposed to trying to
actually replicate DDL at the low level. The latter is better, yes, but
seems to have proven extremely difficult. Hence, why you see the advent of
functions to pipe DDL through the replication stream.

Thanks,
Jeremy