const CommentsSchema = new Schema({
  userId: { type: Schema.Types.ObjectId, ref: 'User', require: true },
  articleId: { type: Schema.Types.ObjectId, ref: 'Article', require: true },
  content: { type: String, require: true },
  created_at: { type: Date, default: Date.now },
  thumbsUp: [{ type: Schema.Types.ObjectId, ref: 'User' }],
  thumbsDown: [{ type: Schema.Types.ObjectId, ref: 'User' }]
})

commentModel = {
  userId: ctx.session.user._id || ctx.request.body.userId,
  articleId: articleId,
  content: content
};

Comments.create(commentModel)

第二次插入数据的时候报错

  name: 'MongoError',
  message: 'E11000 duplicate key error collection: myblog.comments index: thumbsUp_1 dup key: { : undefined }',
  driver: true,
  code: 11000,
  index: 0,
  errmsg: 'E11000 duplicate key error collection: myblog.comments index: thumbsUp_1 dup key: { : undefined }',
  getOperation: [Function],
  toJSON: [Function],
  toString: [Function] }

请问该如何解决