Explanation:Only the OP_QUERY and OP_GET_MORE messages result in a response from the database. 5. Point out the correct statement :
A. An equality match on the unique _id field is less selective as it can match at most one document
B. The selectivity of regular expressions depends on the expressions themselves
C. Less selective queries can use indexes effectively or even at all
D. All of the mentioned
Answer:A
Explanation:Only the OP_QUERY and OP_GET_MORE messages result in a response from the database. 5. Point out the correct statement :
A. An equality match on the unique _id field is less selective as it can match at most one document B. The selectivity of regular expressions depends on the expressions themselves C. Less selective queries can use indexes effectively or even at all D. All of the mentioned
Explanation:If an index exists for the field, then MongoDB matches the regular expression against the values in the index, which can be faster than a collection scan. 6. _____ can modify specific fields of an existing document or documents or replace an existing document entirely, depending on the update parameter.