Re: Initial Schema Sync for Logical Replication

On 2023-Mar-15, Kumar, Sachin wrote:

> 1. In CreateSubscription() when we create replication slot(walrcv_create_slot()), should
> use CRS_EXPORT_SNAPSHOT, So that we can use this snapshot later in the pg_dump.
>
> 2. Now we can call pg_dump with above snapshot from CreateSubscription.

Overall I'm not on board with the idea that logical replication would
depend on pg_dump; that seems like it could run into all sorts of
trouble (what if calling external binaries requires additional security
setup? what about pg_hba connection requirements? what about
max_connections in tight circumstances?).

It would be much better, I think, to handle this internally in the
publisher instead: similar to how DDL sync would work, except it'd
somehow generate the CREATE statements from the existing tables instead
of waiting for DDL events to occur. I grant that this does require
writing a bunch of new code for each object type, a lot of which would
duplicate the pg_dump logic, but it would probably be a lot more robust.

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/