-- ROW 关键字生成一个元组
SELECT ROW (1, 2, 3);

-- pg_column_size函数获取存储数据需要的字节数
SELECT pg_column_size(ROW (1,2,3)); -- 36
SELECT pg_column_size(ROW (1::int2, 2::int2, 3::int2)); -- 30
