如何创建在MongoDB中插入新记录后将自动递增的字段？

Question

I'm using Mongoose and Node.js

The Schema of the model is as follows:

let orderSchema = new Schema({
    'product': String,
    'orderNumber': Number,
    'totalPrice': Number,
    'customer': {
        'type': Schema.Types.ObjectId,
        'ref': 'Users'
    });

I want to set the orderNumber as an increamenting integer.

Is there any way to do it in MongoDB?

I don't want to use the pre-hook technique to do it

Answer 1

You need to create a collection with counters and a plugin with two hooks inside:

1. schema.pre - to get the current value of counter
2. schema.post - to save new value of counter

Counter schema will look like this:

const conterSchema = new Schema({
  name: String,
  value: Number
});

While the plugin will can be defined like this:

function incrementOrderNumber (schema) {
  schema.pre('save', next => {
    CounterModel.findOne({ name: 'orderNumberCounter' })
      .then(counterDoc => counterDoc.toObject())
      .then(({ value}) => {
        this.orderNumber = value;
        next();
      });
  });

  schema.post('save', next => {
    CounterModel.findOneAndUpdate({ name: 'orderNumberCounter' }, { $inc: { value: 1 }}).exec();
  });
}

After creating such plugin function you will need to plug it into your schema:

orderSchema.plugin(incrementOrderNumber);

Do not forget to insert orderNumberCounter into counters collection.