MongoDB – How to remove a field from document

By mkyong | Updated: January 29, 2015

Viewed: 735 (+5 pv/w)

Tags: array mongodb remove field

This MongoDB article shows you how to remove a field from document and array.

1. Remove a field from Documents

Sample of document, and you want to remove the field “affLink”.

{
      "_id" : 1,
      "domain" : "mkyong.com",
      "affLink" : "abc"
}

To remove a field from all documents, set {multi: true}, else only the field of the first matched document will be removed.

db.domain.update({},{$unset: {affLink:1}},{multi: true});

Output

{
      "_id" : 1,
      "domain" : "mkyong.com"
}

2. Remove a field from Array

Prior to MongoDB 2.6, there is still no official function to remove a field from the array. To fix it, you need to write a script :

{
   _id: 1,
   name: "mkyong",
   addresses: [
	{
	  street: "99 The Rock Street",
	  city: "Boston",
	  state: "MA",
	  zip: "66666"
	},
	{
	  street: "88 WWF Street",
	  city: "Boston",
	  state: "MA",
	  zip: "77777"
	}
   ]
}

Loop over the documents and remove field “state” from the array one by one.

 
 db.person.find({}).forEach(function(doc) {

	var address = doc.addresses;
	for(var i = 0; i < address.length; ++i) { 
		var x = address[i];
		delete (x["state"]);
		
	}
	db.person.save(doc);

});

Output

{
   _id: 1,
   name: "mkyong",
   addresses: [
	{
	  street: "99 The Rock Street",
	  city: "Boston",
	  zip: "66666"
	},
	{
	  street: "88 WWF Street",
	  city: "Boston",
	  zip: "77777"
	}
   ]
}

References

1. MongoDB : $unset
2. MongoDB : Modify documents
3. MongoDB : Query document, Array