猫鼬：你怎么不来？

Question

I'm using autopopulate , but there's one case where I don't want to populate. How can I unpopulate?

var userSchema = new Schema({
  local: { type: ObjectId, ref: 'Local', autopopulate: true },
  facebook: { type: ObjectId, ref: 'Facebook', autopopulate: true },
  twitter: { type: ObjectId, ref: 'Twitter', autopopulate: true },
  google: { type: ObjectId, ref: 'Google', autopopulate: true }
});

User
  .findById(req.params.id)
  .unpopulate(local)
  .exec()...

Answer 1

As far as my understanding, mongoose-autopopulate is using mongoose middleware pre hook to configure the populate options on find and findOne queries before executing it. It is like implicitly attaching the populate option in the query.

For your schema, with mongoose-autopopulate User.findById(req.params.id) will get converted into

User.findById(req.params.id).populate('local')
.populate('facebook').populate('twitter').populate('google');

And there is no way in mongoose-autopopulate to remove it, until and unless you explicitly disable the autopopulate option for the required field before querying.

The populate function is nothing but an another call to the database to fetch the referenced document and embed it to the main document. So, try avoiding to populate it at first place and not removing it once you have already fetched it.

Answer 2

See https://github.com/mongodb-js/mongoose-autopopulate/issues/7 .

var numCalls = 0;
var optionsFunction = function() {
  ++numCalls;
  return false;
};

var bandSchema = new Schema({
  name: String,
  lead: { type: ObjectId, ref: 'people', autopopulate: optionsFunction }
});
bandSchema.plugin(autopopulate);

var Band = mongoose.model('band5', bandSchema, 'bands');
Band.findOne({ name: "Guns N' Roses" }, function(error, doc) {
  // `doc.lead` won't be populated because optionsFunction() is falsy
});