How to implement Row Level Security in Postgres?

-- Enable row-level security on the messages table
ALTER TABLE messages ENABLE ROW LEVEL SECURITY;

-- Create a policy that allows users to access only their own messages
CREATE POLICY messages_user_policy
  FOR ALL
  USING (current_setting('app.user_id')::text = chat_id);

-- Set the current user ID when connecting to the database
SET app.user_id = 'user1';

-- Now, when querying the messages table, only messages belonging to 'user1' will be returned
SELECT * FROM messages;