Cursor can return objects out of order if updated during query ("legacy" readMode only)

var t = db.foo; t.drop(); t.ensureIndex({a: 1, b: 1}); t.insert({a: 1, b: 3}); t.insert({a: 2, b: 2}); t.insert({a: 3, b: 1}); var cur = t.find({a: {$lt: 4}}).sort({b: -1}).batchSize(2); printjson(cur.next()); printjson(cur.next()); t.update({b: 1}, {$set: {b: 4}}); printjson(cur.next()); // prints {a: 3, b: 4}, which is out of order