It does not support the update, upsert, or sparse-lookup operations.

它不支持更新、更改插入或稀疏查找操作。

Only the fields in the object that are qualified for the UPSERT operation are displayed.

该对象中只显示适合 UPSERT 操作的字段。

The upsert iterator is the one that performs the actual updates or inserts and deletes.

迭代器 upsert 执行实际的更新或者插入及删除操作。

Merge also replaces the client-side logic known as upsert that performs conditional updates and inserts.

Merge 还替换了执行条件更新与插入客户端逻辑 upsert。