c++ - 想要更新结果

Question

我正在更新一个集合:

conn->update("mycollection", BSON("_id" << ID), BSON("$set" << BSON("myfiled" << myvalue)));

有没有办法知道集合是否真的更新了？ “update”函数无效，没有抛出异常。即使没有数据写入数据库，函数 GetLastError 也返回空字符串。

Answer 1

来自 MongoDB 文档:

Write concern describes the guarantee that MongoDB provides when reporting on the success of a write operation. The strength of the write concerns determine the level of guarantee. When inserts, updates and deletes have a weak write concern, write operations return quickly. In some failure cases, write operations issued with weak write concerns may not persist. With stronger write concerns, clients wait after sending a write operation for MongoDB to confirm the write operations.

我没有使用 C++ 驱动程序，但在 Java 驱动程序中有一个 WriteConcern允许您控制操作的类。您可以检查 C++ 驱动程序中的等效类。

有关 Write Concern 的更多信息，请查看 here .