The current behaviour for upserts and delete commands is that they need to specify full shard key in the query. If not we fail on mongos.

• This is an unnecessary holdover from the time where we could only target a single shard if we had an exact match on the shard key
• The real requirement for upsert and non-multi delete is not an exact shard key match, but rather that the operation can target a single shard
• It is unnecessary to make exact shard key a special requirement, because agnostically targeting the query can resolve to a single shard even with a partial or range query on the shard key, if all relevant chunks are on the same shard
• Removing this requirement will help the ongoing project to make sharding more transparent, by removing a cluster-only special case that is not enforced for a replica set deployment