_id field is automatically generated, but if directing a saved object contained in the id field, using the object id value and will not be automatically generated,
But id the meaning of this field in a different table it may not be the same, there is no guarantee that it must be the only, so save in the case of repeated id to mongo complains,
Excuse me how should handle? Please bosses glad ~ ~

CodePudding user response:

Your question is a little abstract

CodePudding user response:

Can extend this id let its only in different tables