Feedback-ID: ia2694551:Fastmail
Date: Sat, 18 Mar 2023 13:06:38 +0100
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: "Kumar, Sachin" <ssetiya@amazon.com>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Subject: Re: Initial Schema Sync for Logical Replication
Message-ID: <20230318120638.3z7usvxwncs47tdy@alvherre.pgsql>
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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/