Hi Ross,

I actually just found out the problem.

Even if I put replaceDocument to writeConfig:

val writeConfig = WriteConfig(Map("uri" -> s"mongodb://$host/$database.$table", "replaceDocument" -> "false"))

If I use:

MongoSpark.save(data.write.mode("append"), writeConfig)

It will not work, because this function call the dataFrameWriter from Spark and doesn't take account of the mongodb writeConfig options. Instead I should use:

MongoSpark.save(data, writeConfig)

This will call the correct MongoSpark writer function.

I think this point should be noted in the document because it is indeed confusing.

Regards,
Thang

https://groups.google.com/d/msg/mongodb-user/eF-qdpYbFS0/KNqDB2vJAwAJ