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Listen and Notify in Postgres

Brandur Leach shows how to use PostgreSQL’s listen/notify capabilities:

Listen/notify in Postgres is an incredible feature that makes itself useful in all kinds of situations. I’ve been using it a long time, started taking it for granted long ago, and was somewhat shocked recently looking into MySQL and SQLite to learn that even in 2024, no equivalent exists.

In a basic sense, listen/notify is such a simple concept that it needs little explanation. Clients subscribe on topics and other clients can send on topics, passing a message to each subscribed client. The idea takes only three seconds to demonstrate using nothing more than a psql shell:

Read on to learn more about the notifier pattern. What’s interesting is that the notifier patter, which adds a fair bit of structure to this very simple process, makes it work a good bit like SQL Server’s Service Broker.