在 Postgresql 中实现自定义运算符时出错

在我的Postgres扩展pg_sample_ext中创建一个简单的Custom操作符，但在数据库中实现它时遇到错误.下面提到了更新脚本和错误的代码.

Update script pg_sample_ext--1.0.1--1.0.2.sql:

-- Create necessary objects for version 1.0.2

-- Custom Operator: @*
-- Description: Custom operator that multiplies two values of type my_type

-- Create a new type to use in our operator.
CREATE TYPE my_type AS (value int);

-- Create a SQL function that defines the behaviour of the custom operator.
-- This function multiplies the values of two my_type operands.
CREATE FUNCTION multiply_values(left my_type, right my_type) RETURNS my_type AS $$
    SELECT ROW((left.value * right.value))::int;
$$ LANGUAGE SQL IMMUTABLE;

-- Create a custom operator that multiplies two values of type my_type.
-- The operator symbol is @*.
-- It takes two operands of type my_type and returns a value of the same type.
-- The behaviour is defined by the SQL function multiply_values.
CREATE OPERATOR @* (
    PROCEDURE = multiply_values,
    LEFTARG = my_type,
    RIGHTARG = my_type
);

错误:

spartacus=# SELECT ROW(2)::my_type @* ROW(3)::my_type AS result;
错误:  syntax error at or near "."
LINE 2:     SELECT ROW((left.value * right.value))::my_type;
                        ^
QUERY:
    SELECT ROW((left.value * right.value))::my_type;

CONTEXT:  SQL function "multiply_values" during inlining