Which of the following index would be optimum for the query?
Select all valid. db.test.find( { a : 5, c : 2 })
db.test.ensurelndex( { c:l, a: 1})
db.test.ensurelndex( { a : 1, c: 1, d: 1, b : 1})
CH db.test.ensurelndex( { a :1, c:l})
db.test.ensurelndex( { a: 1, b :1, c:l, d:l})
Submit