我在尝试减去两个日期以获得毫秒数差异时遇到了Mongoose聚合问题。文档结构如下:DeliverySchema=newmongoose.Schema({hash:String,status:Number,insertedOn:{type:Date,default:Date.now},endedOn:{type:Date}},{collection:'Deliveries'});这是查询:varDelivery=mongoose.model('Delivery');returnDelivery.aggregate([{$match:{'insertedOn':{$ne:null,$ty