What is the "__v" field in Mongoose What is the "__v" field in Mongoose mongoose mongoose

What is the "__v" field in Mongoose

From here:

The versionKey is a property set on each document when first created by Mongoose. This keys value contains the internal revision of the document. The name of this document property is configurable. The default is __v.

If this conflicts with your application you can configure as such:

new Schema({..}, { versionKey: '_somethingElse' })

Well, I can't see Tony's solution...so I have to handle it myself...

If you don't need version_key, you can just:

var UserSchema = new mongoose.Schema({    nickname: String,    reg_time: {type: Date, default: Date.now}}, {    versionKey: false // You should be aware of the outcome after set to false});

Setting the versionKey to false means the document is no longer versioned.

This is problematic if the document contains an array of subdocuments. One of the subdocuments could be deleted, reducing the size of the array. Later on, another operation could access the subdocument in the array at it's original position.

Since the array is now smaller, it may accidentally access the wrong subdocument in the array.

The versionKey solves this by associating the document with the a versionKey, used by mongoose internally to make sure it accesses the right collection version.

More information can be found at: http://aaronheckmann.blogspot.com/2012/06/mongoose-v3-part-1-versioning.html

For remove in NestJS need to add option to Shema() decorator

@Schema({ versionKey: false })