removing an object from a mongodb document

Question

I have a document in Mongodb collection, where I want to remove an object, using title key.

I tried using $unset, but it only removes the title key not the object to which it belongs.

{
    "_id" : ObjectId("576b63d49d20504c1360f688"),
    "books" : [
        {
            "art_id" : ObjectId("574e68e5ac9fbac82489b689"),
            "title" :"abc",
            "price" : 40
        },
        {
            "art_id" : ObjectId("575f9badada0500d192c53f4"),
            "title" : "xyz",
            "price" : 20
        },
        {
            "art_id" : ObjectId("57458224d86b3d1561150f17"),
            "title" : "def",,
            "price" : 30
        }
    ],
    "user_id" : "575570c315e27d13167dfc0d"
}

score 3 · Accepted Answer · edited May 23 '17 at 12:02

To remove the entire object that contains the query object use db.remove() query.

For your case:

db.yourcollection.remove({"books.title": "abc"});

Please double check the format in which the element of array is referenced. This removes the entire objects that contains the embedded query obj. To remove only a single object, provide it with another field to uniquely identify it.

If you only want to remove the object that contains the title field from the array but wants to keep the object that contains the array, then please use the $pull operator. This answer will be of help.

Example: if you want to remove object

        {
            "art_id" : ObjectId("574e68e5ac9fbac82489b689"),
            "title" :"abc",
            "price" : 40
        }

just from the array but keep the parent object like

{
    "_id" : ObjectId("576b63d49d20504c1360f688"),
    "books" : [
        {
            "art_id" : ObjectId("575f9badada0500d192c53f4"),
            "title" : "xyz",
            "price" : 20
        },
        {
            "art_id" : ObjectId("57458224d86b3d1561150f17"),
            "title" : "def",,
            "price" : 30
        }
    ],
    "user_id" : "575570c315e27d13167dfc0d"
}

use

db.mycollection.update(
    {'_id': ObjectId("576b63d49d20504c1360f688")}, 
    { $pull: { "books" : { "title": "abc" } } },
false,
true 
);

score 2 · Answer 2 · answered Jun 23 '16 at 05:12

$unset won't remove the object from an array. The $unset operator deletes a particular field. doc.

Use $pull instead.

The $pull operator removes from an existing array all instances of a value or values that match a specified condition.

Try following query

db.collName.update({$pull : {books:{title:abc}}})

Refer $pull-doc

Hope this will help you.

score 1 · Answer 3 · answered Aug 31 '18 at 14:34

And if... ¿Do I want to delete an object that is inside a document and not as an array?

{
    "_id" : ObjectId("576b63d49d20504c1360f688"),
    "books" : {
        "574e68e5ac9fbac82489b689": {
            "art_id" : ObjectId("574e68e5ac9fbac82489b689"),
            "title" :"abc",
            "price" : 40
        },
        "575f9badada0500d192c53f4": {
            "art_id" : ObjectId("575f9badada0500d192c53f4"),
            "title" :"xyz",
            "price" : 20
        },
        "57458224d86b3d1561150f17": {
            "art_id" : ObjectId("57458224d86b3d1561150f17"),
            "title" : "def",
            "price" : 30
        }
    },
    "user_id" : "575570c315e27d13167dfc0d"
}

The solutions is this:

db.auctions.update(
    {'_id': ObjectId("576b63d49d20504c1360f688")},
    {$unset: {"books.574e68e5ac9fbac82489b689":
        {_id: "574e68e5ac9fbac82489b689"}}})

score 0 · Answer 4 · answered Jun 23 '16 at 05:03

Try using pull.

https://docs.mongodb.com/manual/reference/operator/update/pull/

$pull

The $pull operator removes from an existing array all instances of a value or values that match a specified condition.

The $pull operator has the form:

{ $pull: { <field1>: <value|condition>, <field2>: <value|condition>, ... } }

To specify a <field> in an embedded document or in an array, use dot notation.

score 0 · Answer 5 · answered Jun 23 '16 at 05:14

0

Try in the mongo shell

db.yourcollection.remove({books:[{title:'title_you_want'}]})

Careful with the braces.

answered Jun 23 '16 at 05:14

Thishani Lucas

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I don't think this will work. I think you need to reference title as {"books.title": "abc"} – Nidhin David Jun 23 '16 at 10:06

removing an object from a mongodb document

5 Answers5