memset(((C*)x) + old_data_bytes, 0, old_data_bytes - data_bytes);
第一层是上游“卖铲子”的硬件基础设施供应商，核心逻辑是提供淘金必需的”工具”，稳稳赚取技术红利。
。爱思助手下载最新版本对此有专业解读
Union is our own "style engine" on top of these two. Instead of having
https://portavita.github.io/2018-10-31-blog_A_JSON_use_case_comparison_between_PostgreSQL_and_MongoDB/