Explanation:If the query planner cannot obtain the sort order from an index, it will sort the results in memory. 5. Point out the correct statement :
A. If you only ever query on a single key in a given collection, then you need to create just multikey index for that collection
B. If you sometimes query on only one key and at other times query on that key combined with a second key, then creating a compound index is more efficient than creating a single-key index
C. The choice between creating compound indexes that support your queries or relying on index intersection is independent of specifics of your system
D. None of the mentioned
Answer:A
Explanation:If the query planner cannot obtain the sort order from an index, it will sort the results in memory. 5. Point out the correct statement :
A. If you only ever query on a single key in a given collection, then you need to create just multikey index for that collection B. If you sometimes query on only one key and at other times query on that key combined with a second key, then creating a compound index is more efficient than creating a single-key index C. The choice between creating compound indexes that support your queries or relying on index intersection is independent of specifics of your system D. None of the mentioned
Explanation:MongoDB will use the compound index for both queries. 6. An index can support sort operations on a non-prefix subset of the index key pattern using _________ condition.