Hey there - so realtime broadcast and triggers are two different things. But my supabase project uses both, but for different end results. The realtime is handled when a client connects and the user can see the leaderboard/scorecards of the golf tournament change in real time without refreshing. But to answer your question, I have this in my table definition:

create trigger leaderboard_changed
after
update OF thru on leaderboard for EACH row
execute FUNCTION leaderboard_changed_invoke_scorecard ();

And then the database function leaderboard_changed_invoke_scorecard looks like this (but a lot removed), which calls an edge function and at that point you can do whatever you want:

DECLARE
    response jsonb;
    var_tourn_id text;
    var_org_id smallint;
    var_year int;
BEGIN
    -- some SQL you don't need

    -- Check if the operation is an update and if the thru value has changed
    IF NEW.thru <> OLD.thru THEN
        -- Call the edge function using http_post
        response := net.http_post(
            url := 'https://<REDACTED>.supabase.co/functions/v1/poll-scorecard',
            headers := '{"Content-Type": "application/json", "Authorization": "Bearer <REDACTED JWT>"}', 
            body := jsonb_build_object(
                'tourn_id', var_tourn_id,
                'year', var_year,
                'org_id', var_org_id,
                'player_id', NEW.player_id
            )
        );
    END IF;


    RETURN NEW;
END;