Subscription

Subscription is the object that, on the subscriber side (the target database), establishes the connection to the PostgreSQL publisher, specifies which publication to subscribe to, and manages the full lifecycle of logical replication: initial data snapshot, streaming of incremental changes, automatic reconnection on disconnect.

How to create one #

You declare it with CREATE SUBSCRIPTION, providing the connection to the publisher and the publication to consume:

CREATE SUBSCRIPTION my_sub
  CONNECTION 'host=pg-primary user=replica_user dbname=app'
  PUBLICATION my_pub;

On creation, an initial snapshot of the tables is taken, then continuous WAL streaming begins.

State and monitoring #

The pg_stat_subscription view exposes the state of every active subscription: current apply position, lag, last received event. It’s the entry point for troubleshooting replication lag or stalls.

Operational limits #

A subscription cannot be natively paused/resumed before version 14 — it can only be disabled with ALTER SUBSCRIPTION ... DISABLE. On conflicts (row already present on the target, constraint violations) the stream stops and must be resolved manually before it resumes.