elasticsearch从mysql导出数据并建立嵌套数据类型怎么做呢？

elasticsearchwriter从mysqlreader中导出数据，例如现在mysql中有id，name，num1，num2四列，导入到es中的数据结构需要是
{
"id": "",
"name": "",
"visits": [{
"num1": "",
"num2": ""
}]
}
这样，其中visits是在mysql中没有的，将num1，num2导出进去，并形成一个嵌套的结构，请问怎么实现呀？

The issue mentions elasticsearchwriter and mysqlreader; start by checking their supported field-mapping and transformation options. Confirm whether nested visits output is supported and document a reproducible configuration or identify the missing capability.

Written by the indexing model from the issue text.