Set timestamp on nested document but not on parent document in Mongoose

Question

I have a Mongoose schema where I'm using the timestamps option to automatically add createdAt and updatedAt fields to documents. However, I want to apply timestamps only to the subdocuments, not to the main document.

Here's an example of my schema:

const feedSchema = new mongoose.Schema(
  {
    userId: {
      type: String,
      required: true,
    },
    feed: [
      new mongoose.Schema(
        {
          // ... (subdocument fields)
        },
        { _id: false, timestamps: true } }
      ),
    ],
  },
  {
    _id: false,
    timestamps: false,
    versionKey: false,
  }
);

The issue is that even though I've set timestamps: true only for the subdocument schema, Mongoose is still adding timestamps to the main document, even though I disabled them.

Is there a way to configure Mongoose to apply timestamps only to the subdocuments within the feed array and not to the main document?

Answer 1

The best way around this is - don't use Model.create() to create your documents and instead use new Model() combined with doc.save(). That will allow you to pass in the {timestamps: false} option when you call save(). Here is an example:

const feedSchema = new mongoose.Schema(
  {
    userId: {
      type: String,
      required: true,
    },
    feed: [
      new mongoose.Schema(
        {
          // ... (subdocument fields)
        },
        { _id: false, timestamps: true } }
      ),
    ],
  },
  {
    // _id: false, //< delete this
    timestamps: false,
    versionKey: false,
  }
);

const Feed = mongoose.model('Feed', feedSchema);

const newFeed = {
   userId: '123',
   feed: [
      {
         a: 'abc',
         b: 'xyz'
      }
   ]
};

const doc = new Feed(newFeed);
await doc.save({ timestamps: false });

This will add the timestamps to the subdocuments but not on the parent document.

Note: you will need to delete the _id : false on the parent schema as mongoose documents require an _id before saving.