没有问题，你可以看到索引在那里。你期望它不允许重复元素？为此，您必须将唯一标志设置为true：

There are no problems, you can see that the index is there. You're expecting it not to allow duplicate elements? For that you have to set unique flag to true:

db.users.ensureIndex({ name : 1},{unique: true});

更新：使用 {unique：true}再次运行确保不起作用，你必须再次放弃 ensureIndex ：

UPDATE: running ensure once again with {unique: true} doesn't work, you have to drop and ensureIndex again:

db.users.dropIndex({name:1})
db.users.ensureIndex({ name : 1}, {unique:true, dropDups : true});