Why should you care?

PostgresVerse migrates orders table to new PG major on subscriber while other tables stay on old primary during cutover window.

See it live — copy this example

Run in pgAdmin or psql.

CREATE PUBLICATION orders_pub FOR TABLE orders;

-- On subscriber (connected to publisher)
CREATE SUBSCRIPTION orders_sub
CONNECTION 'host=primary.db.local dbname=PostgresVerse user=repl password=***'
PUBLICATION orders_pub;

What happened?

• Publication names tables to replicate.
• Subscription on downstream connects upstream and applies changes.
• Only orders flow — not whole cluster.

Practice next

1. Set wal_level=logical on publisher.
2. CREATE PUBLICATION for one table.
3. CREATE SUBSCRIPTION on second instance.
4. ADD TABLE order_items TO PUBLICATION orders_pub;
5. Check lag: SELECT * FROM pg_stat_subscription;

Remember

Publication/subscription model for table-level sync. Requires wal_level logical. Use for migrations, aggregators, and selective fan-out.

PostgresVerse PG16 upgrade

Logical sub replays orders to PG16 cluster; app dual-writes during validation week.

Outcome: Major upgrade without multi-hour downtime window.