Not in covered index query does not have nscannedObjects = 0

testDB = db.getSiblingDB("qa293") var coll = testDB.getCollection("simple.1") coll.drop() for (i=0;i<10;i++) { coll.insert( {foo:i} ) } for (i=0;i<10;i++) { coll.insert( {foo:i} ) } for (i=0;i<5;i++) { coll.insert( {bar:i} ) } coll.insert( {foo:"1"} ) coll.insert({foo:{bar:1}}) coll.insert( {foo:null} ) coll.ensureIndex( {foo:1} ) // Test not in query var plan = coll.find({foo:{$nin: [5,8] }}, {foo:1, _id:0} ).hint( {foo:1} ).explain() assert.eq(true, plan.indexOnly, "simple.1.8 - indexOnly should be true on covered query") assert.eq(0, plan.nscannedObjects, "simple.1.8 - nscannedObjects should be 0 for covered query")