isn't it because mongo has update operation that can do a $set (like SQL) and couchbase doesn't? how else can couchbase update a field in an existing document?
The "CAS" in the OP stands for "Compare and Swap". The complaint is that they had Couchbase checking for read-write conflicts while Mongo was doing blind updates regardless of if the data in Mongo was different from what the client expected.
The complaint isn't about sub-document updates vs. full document updates. The complaint is about conflict checking. Couchbase could have been told to blindly write, but wasn't, and Mongo was told to blindly write.
The complaint isn't about sub-document updates vs. full document updates. The complaint is about conflict checking. Couchbase could have been told to blindly write, but wasn't, and Mongo was told to blindly write.