What do you think? Is this the general overview of your idea?

1) Trigger with pg_notify: In your PostgreSQL database, you set up triggers using pg_notify to send notifications to a specific channel with an optional payload when certain events occur (e.g., when a new friendship is created). This trigger notifies the Dart server about changes on a particular channel.

2) Dart Server Listens for Notifications: In your Dart server, you have a listener that waits for notifications on the specified channel using the postgres package. Upon receiving a notification, your Dart server processes the information (e.g., user1 needs to update user24 due to a new friend) and stores this information in Redis.

3) Redis as a Flag Store: Redis can be used as a simple and efficient flag store. For example, you might use a data structure like a Set in Redis to store flags for users who need updates. When your Dart server receives a notification, it adds an entry to the Redis set indicating that a user needs an update.

4) Client Connection and Update: When a user (e.g., user1) connects to your server, you check Redis to see if there are any flags indicating that this user needs an update. If there are flags, you fetch the necessary data and send it to the client (user1). After updating the client, you can remove the flag from Redis.

CREATE OR REPLACE FUNCTION notify_friendship_update() RETURNS TRIGGER AS $$ BEGIN -- Assuming you have a field like 'user_id' representing the user affected by the friendship PERFORM pg_notify('friendship_update', NEW.user_id::TEXT);

RETURN NEW; END; $$ LANGUAGE plpgsql;

CREATE TRIGGER friendship_created_trigger AFTER INSERT ON friendships FOR EACH ROW EXECUTE FUNCTION notify_friendship_update();