hasura graphql pg 自定义函数的使用

CREATE TABLE sql_function_table (
    id SERIAL PRIMARY KEY,
    input text NOT NULL,
    output text
);

CREATE FUNCTION test_func() RETURNS trigger AS $emp_stamp$
      BEGIN
          NEW.output := UPPER(NEW.input);
          RETURN NEW;
      END;
  $emp_stamp$ LANGUAGE plpgsql;

  CREATE TRIGGER test_trigger BEFORE INSERT OR UPDATE ON sql_function_table
      FOR EACH ROW EXECUTE PROCEDURE test_func();

mutation {
  insert_sql_function_table (
    objects: [
      {input: "dalongdemo!"}
    ]
  ) {
    returning {
      output
    }
  }
}