example audit trigger for django model that inserts to another model

log_transacao_srph.sql

CREATE OR REPLACE FUNCTION log_transacao_srph() RETURNS TRIGGER AS $$
BEGIN
    IF TG_OP = 'UPDATE' THEN
        INSERT INTO sla_mudancastatus (datahora, numero_os, anterior, novo, abertura, orcamento, aprovacao, emissao, cancelamento, reabertura, operador) 
            VALUES(NOW(), NEW.numero_os, OLD.status_viagem, NEW.status_viagem, NEW.abertura, NEW.orcamento, NEW.aprovacao, NEW.emissao, NEW.cancelamento, NEW.reabertura, NEW.operador);
        RETURN NEW;
    END IF;
    IF TG_OP = 'INSERT' THEN
        INSERT INTO sla_mudancastatus (datahora, numero_os, anterior, novo, abertura, orcamento, aprovacao, emissao, cancelamento, reabertura, operador) 
            VALUES(NOW(), '', 'ABE', NEW.status_viagem, NEW.abertura, NEW.orcamento, NEW.aprovacao, NEW.emissao, NEW.cancelamento, NEW.reabertura, NEW.operador);
        RETURN NEW;
    END IF;
END;
$$ LANGUAGE plpgsql;

DROP TRIGGER IF EXISTS audit_srph_status_change ON hal_ordemservico;
CREATE TRIGGER audit_srph_status_change 
AFTER UPDATE ON hal_ordemservico FOR EACH ROW 
WHEN (OLD.status_viagem IS DISTINCT FROM NEW.status_viagem)
EXECUTE PROCEDURE log_transacao_srph();

DROP TRIGGER IF EXISTS audit_srph_status_insert ON hal_ordemservico;
CREATE TRIGGER audit_srph_status_insert 
AFTER INSERT ON hal_ordemservico FOR EACH ROW 
EXECUTE PROCEDURE log_transacao_srph();

DROP FUNCTION log_transacao;