函数的结果会以 CLOB（字符型大型对象）数据类型的形式返回，可容纳 1 MB 的数据。

The result of the function is returned as a CLOB (Character Large Object) data type that can hold up to 1 MB of data.

youdao

这种序列化方式强行在写入一个字符之前在内存中建立整个对象的字符串表示，对于大型对象来说，这是个非常大的性能拖累。

This approach to serialization forces a string representation of the entire object to be created in memory before a single character can be written, which is a big performance drag for large objects.

youdao