Specifies the number of documents to return in each batch of the response from the MongoDB instance. In most cases, modifying the batch size will not affect the user or the application, as the mongo shell and most drivers return results as if MongoDB returned a single batch.
The batchSize() method takes the following parameter:
Parameter Description size The number of documents to return per batch. Do not use a batch size of 1.
Specifying 1 or a negative number is analogous to using the limit() method.