Postgres logs using trigger

Table to save logs

CREATE TABLE clientes (
    id serial NOT NULL
        CONSTRAINT clientes_pk
            PRIMARY KEY,
    name varchar(200) NOT NULL,
    data_nascimento date,
    cpf varchar(14) NOT NULL,
    renda_mensal numeric(12, 2),
    ativo boolean DEFAULT TRUE NOT NULL
);

Log Table

CREATE TABLE logs (
    id serial NOT NULL
        CONSTRAINT logs_pk
            PRIMARY KEY,
    tablename varchar(255) NOT NULL,
    old jsonb,
    new jsonb,
    date timestamp DEFAULT NOW() NOT NULL,
    query text NOT NULL,
    action char NOT NULL CHECK (action IN ('I','D','U')),
    schema varchar(255) NOT NULL,
    database_user varchar(255) NOT NULL
);

Json diff to increase the trigger function

CREATE OR REPLACE FUNCTION json_diff(l JSONB, r JSONB) RETURNS JSONB AS
$json_diff$
    SELECT jsonb_object_agg(a.key, a.value) FROM
        ( SELECT key, value FROM jsonb_each(l) ) a LEFT OUTER JOIN
        ( SELECT key, value FROM jsonb_each(r) ) b ON a.key = b.key
    WHERE a.value != b.value OR b.key IS NULL;
$json_diff$
    LANGUAGE sql;

Trigger

CREATE OR REPLACE function public.log() returns trigger
    language plpgsql
as
$$
DECLARE
    old_data jsonb;
    new_data jsonb;
BEGIN
    IF (TG_OP = 'UPDATE') THEN
        IF OLD is distinct from NEW THEN
            old_data = row_to_json(OLD);
            new_data = row_to_json(NEW);

            INSERT INTO public.logs (schema,tablename,database_user,action,old,new,query)
            VALUES (
                    TG_TABLE_SCHEMA::TEXT,
                    TG_TABLE_NAME::TEXT,
                    session_user::TEXT,
                    'U',
                    json_diff(old_data, new_data),
                    json_diff(new_data, old_data),
                    current_query()
            );
        END IF;

        RETURN NEW;
    ELSIF (TG_OP = 'DELETE') THEN
        old_data = row_to_json(OLD);

        INSERT INTO public.logs (schema,tablename,database_user,action,old,query)
        VALUES (
                TG_TABLE_SCHEMA::TEXT,
                TG_TABLE_NAME::TEXT,
                session_user::TEXT,
                'D',
                old_data,
                current_query()
        );
        RETURN OLD;
    ELSIF (TG_OP = 'INSERT') THEN
        new_data = row_to_json(NEW);
        INSERT INTO public.logs (schema,tablename,database_user,action,new,query)
        VALUES (
                TG_TABLE_SCHEMA::TEXT,
                TG_TABLE_NAME::TEXT,
                session_user::TEXT,
                'I',
                new_data,
                current_query()
        );
        RETURN NEW;
    END IF;
END;
$$;

Define trigger in table

CREATE TRIGGER trigge_log
    AFTER INSERT OR UPDATE OR DELETE
    ON clientes
    FOR EACH ROW
EXECUTE PROCEDURE log();

Definindo variáveis de sessão no postgres para utilização nas triggers

SET SESSION "application.user_id" = 366; -- setando

SELECT current_setting('application.user_id') AS value; -- resgatando