Delete a key from a MongoDB document using Mongoose

Question

I'm using the Mongoose Library for accessing MongoDB with node.js

Is there a way to remove a key from a document? i.e. not just set the value to null, but remove it?

User.findOne({}, function(err, user){
  //correctly sets the key to null... but it's still present in the document
  user.key_to_delete = null;

  // doesn't seem to have any effect
  delete user.key_to_delete;

  user.save();
});

Sihonn

I thought I had found it, but after some tests: probably not. This has some good discussion on the topic though. groups.google.com/group/mongoose-orm/browse_thread/thread/… – Audrit

LOL nevermind, I guess this was your post! – Audrit

Answer 1

In early versions, you would have needed to drop down the node-mongodb-native driver. Each model has a collection object that contains all the methods that node-mongodb-native offers. So you can do the action in question by this:

User.collection.update({_id: user._id}, {$unset: {field: 1 }});

Since version 2.0 you can do:

User.update({_id: user._id}, {$unset: {field: 1 }}, callback);

And since version 2.4, if you have an instance of a model already you can do:

doc.field = undefined;
doc.save(callback);

Silver

This has been fixed in Mongoose 2.X, so you can leave the collection out. – Silver

What's the fix? How does one do it. I've read the docs I have. – Darg

Either use User.update({ _id: id }, { $unset: { field: 1 }}, callback) or if you have a document instance, set the path to undefined and then save it: doc.field = undefined; doc.save() – Alternant

Just a note that if you're trying to remove an old property that's no longer defined in your schema you need to do doc.set('field', undefined) – Shedevil

what about deleting doc.field.foo ? – Dermot

Will it work if this key is an object? I.e embedded doc, or am i need to set each property of this object to undefined individualy? – Welsh

@Dermot delete has no effect in v 4.0.2. I guess it makes sense that you wouldn't be allowed to remove properties from a model but seems like it should just have the same effect as setting to undefined. – Corcovado

@Shedevil doc.set('field', undefined) might not be enough since strict mode (default) does not allow to set fields which are not in the schema anymore. doc.set('field', undefined, { strict: false }) worked fine. – Hodometer

@AlexanderLink I tried strict: false as you posted, Keystone recorded that the update was performed but the field is still there... – Phyle

@AlexanderLink where are you doing the doc.set? Thanks. – Riot

Thank you @AlexanderLink I've spent 2 hours looking for this. you are a hero! – Kabuki

none of the other comments work. it should be something like this: User.updateOne({ _id: user._id }, { $unset: { field: 1 }}, { strict: false }). – Ful

Answer 2

You'll want to do this:

User.findOne({}, function(err, user){
  user.key_to_delete = undefined;
  user.save();
});

Chickadee

That will just set it to null - not what the OP is asking for. – Ethylene

As of version 2.4.0 setting a document key to undefined will pass the $unset to mongodb aaronheckmann.posterous.com/mongoose-240 – Mev

Answer 3

I use mongoose and using any of the above functions did me the requirement. The function compiles error free but the field would still remain.

user.set('key_to_delete', undefined, {strict: false} );

did the trick for me.

Mahratta

Upvoting this useful answer, too bad @alexander-link didn't make it an answer back in 2015 (#4487426) – Torrential

Thank you for your answer, for me, the other solutions did not work for objects nested in arrays! – Mowery

@Mowery This was my case, too. Only this solution worked well because I had to delete a field with array after finding a specific document's id – Iggie

Note that the string is a path to the key. So, if the object you want to delete is nested, you must path to it. This answer solved my problem! – Harmonica

Answer 4

At mongo syntax to delete some key you need do following:

{ $unset : { field : 1} }

Seems at Mongoose the same.

Edit

Check this example.

Gaia

Can you clarify this answer and give a code example that relates to the example code above? – Sihonn

sorry but i am not expereinced at mongoose. Above syntax it's mongo syntax, so i suppose that driver for any language support this. I found some example, check it in my answer. – Gaia

Answer 5

if you want to remove a key from collection try this method.

 db.getCollection('myDatabaseTestCollectionName').update({"FieldToDelete": {$exists: true}}, {$unset:{"FieldToDelete":1}}, false, true);

Doublestop

I don't believe the question was about removing the field from all documents in the collection, which is what this does – Aras

Answer 6

Try:

User.findOne({}, function(err, user){
  // user.key_to_delete = null; X
  `user.key_to_delete = undefined;`

  delete user.key_to_delete;

  user.save();
});

Inexistent

Answer 7

Could this be a side problem like using

function (user)

instead of

function(err, user)

for the find's callback ? Just trying to help with this as I already had the case.

Tennison

Answer 8

Mongoose document is NOT a plain javascript object and that's why you can't use delete operator.(Or unset from 'lodash' library).

Your options are to set doc.path = null || undefined or to use Document.toObject() method to turn mongoose doc to plain object and from there use it as usual. Read more in mongoose api-ref: http://mongoosejs.com/docs/api.html#document_Document-toObject

Example would look something like this:

User.findById(id, function(err, user) {
    if (err) return next(err);
    let userObject = user.toObject();
    // userObject is plain object
});

Menedez

Answer 9

the problem with all of these answers is that they work for one field. for example let's say i want delete all fields from my Document if they were an empty string "". First you should check if field is empty string put it to $unset :

function unsetEmptyFields(updateData) {
  const $unset = {};
  Object.keys(updatedData).forEach((key) => {
    if (!updatedData[key]) {
      $unset[key] = 1;
      delete updatedData[key];
    }
  });
  updatedData.$unset = $unset;

  if (isEmpty(updatedData.$unset)) { delete updatedData.$unset; }

  return updatedData;
}

function updateUserModel(data){
const updatedData = UnsetEmptyFiled(data);

    const Id = "";
    User.findOneAndUpdate(
      { _id: Id },
      updatedData, { new: true },
    );
}

Undermost

Answer 10

you can use delete user._doc.key

Dumbarton