Beginner LevelPostgreSQL
How do LISTEN and NOTIFY provide lightweight database Pub/Sub messaging?
❓ Interview Prompt: Explain `NOTIFY channel, payload`, `LISTEN channel`, asynchronous notification queues, and building real-time websockets with Postgres.
PostgreSQL includes native LISTEN / NOTIFY pub/sub messaging:
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'NOTIFY channel_name, 'payload_string'': Broadcasts an event string over a named channel.
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'LISTEN channel_name': Subscribes a client connection to receive real-time asynchronous event payloads without polling!
Code Implementation Example
sql
-- Broadcast event notification on 'order_updates' channel
NOTIFY order_updates, '{"order_id": 1052, "status": "PAID"}';
-- In subscriber connection:
LISTEN order_updates;💡Broadcasting Pub/Sub notifications via NOTIFY.
🎯 Interview Key Takeaway
Use LISTEN / NOTIFY to trigger real-time application updates directly from database triggers without polling.
#LISTEN#NOTIFY#PubSub#Messaging#Beginner
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