Using MongoDB $pull to delete documents within an Array

Question

I have a collection in MongoDB, which is like following:

{
    "_id" : "5327010328645530500",
    "members" : [
        {
            "participationCoeff" : 1,
            "tweetID" : "5327010328645530500"
        },
        {
            "participationCoeff" : 1,
            "tweetID" : "2820402625046999289"
        },
        {
            "participationCoeff" : 0.6666666666666666,
            "tweetID" : "6122060484520699114"
        },
        {
            "participationCoeff" : 1,
            "tweetID" : "4656669980325872747"
        }
    ]
}
{
    "_id" : "2646953848367646922",
    "members" : [
        {
            "participationCoeff" : 1,
            "tweetID" : "2646953848367646922"
        },
        {
            "participationCoeff" : 0.75,
            "tweetID" : "7750833069621794130"
        },
        {
            "participationCoeff" : 0.5,
            "tweetID" : "6271782334664128453"
        }
    ]
}

Basically, collection have clusters, where a cluster has an _id field and a members field. Members field is an array of documents, having following format.

{
            "participationCoeff" : 1,
            "tweetID" : "5327010328645530500"
        }

Now, from time to time, I have to delete these sub-documents in members attribute of cluster document, by matching tweetID.

However, I'm not able to find a query to achieve this effect. Basically, a tweetID will participate in many clusters, and hence will appear in multiple sub-documents of 'members' attribute of various clusters. I want to supply a bulk $pull operation, where I can remove all the sub-documents in all the clusters (i.e. their members attribute) which match on a particular tweetID.

Some help and intuition will be really helpful.

score 47 · Accepted Answer · answered Feb 27 '13 at 20:44

47

That's exactly what the $pull operator does, so in the shell you could use an update like:

db.clusters.update({}, 
    {$pull: {members: {tweetID: '5327010328645530500'}}}, 
    {multi: true})

Set the multi option so that every document is updated, not just the first one.

answered Feb 27 '13 at 20:44

JohnnyHK

305,182
66
621
471

1

getting following error. `Cannot apply $pull/$pullAll modifier to non-array` – VaidAbhishek Feb 27 '13 at 20:53
1

@VaidAbhishek That means that you have some docs in the collection where `members` isn't an array. – JohnnyHK Feb 27 '13 at 20:56
I don't think that is the case with my collection. members will be a strictly array type attribute of cluster. Is there any way of doing this using aggregation! – VaidAbhishek Feb 27 '13 at 21:01
1

@VaidAbhishek Are you sure? Even if `members` is `null` in a doc that would cause this error as that's not an array. – JohnnyHK Feb 27 '13 at 21:05
I don't think that is the case :-( – VaidAbhishek Feb 28 '13 at 07:31

score 10 · Answer 2 · edited Aug 30 '18 at 15:53

This will delete multiple tweets in a single query just pass an array to $in:-

db.clusters.update({}, 
{$pull: {members: {$in: [ {tweetID: '5327010328645530500'},{"tweetID" : "2820402625046999289"} ] } } }, 
{multi: true});

The above method doesnt work in mongoose so for mongoose do:-

 db.clusters.update({}, 
{$pull: {members:[ {tweetID: '5327010328645530500'},{"tweetID" : "2820402625046999289"} ]  } });

stefano · Answer 3 · 2020-11-28T12:52:08.653

4

In the meantime the update method is deprecated. Therefore one possible up-to-date solution to this would be using the updateMany method instead.

db.clusters.updateMany({}, 
    {$pull: {members: {tweetID: '5327010328645530500'}}})

edited Nov 28 '20 at 12:52

answered Jun 14 '20 at 12:14

stefano

315
2
16

score 2 · Answer 4 · edited Jun 23 '21 at 15:17

NOTE: Used in "mongoose": "^5.12.13".

As for today June 22nd, 2021, you can use $in and $pull mongodb operators to remove items from an array of documents :

Parent Document :

{
    "name": "June Grocery",
    "description": "Remember to pick Ephraim's favorit milk",
    "createdDate": "2021-06-09T20:17:29.029Z",
    "_id": "60c5f64f0041190ad312b419",
    "items": [],
    "budget": 1500,
    "owner": "60a97ea7c4d629866c1d99d1",
}

Documents in Items array :

{
    "category": "Fruits",
    "bought": false,
    "id": "60ada26be8bdbf195887acc1",
    "name": "Kiwi",
    "price": 0,
    "quantity": 1
},
{
    "category": "Toiletry",
    "bought": false,
    "id": "60b92dd67ae0934c8dfce126",
    "name": "Toilet Paper",
    "price": 0,
    "quantity": 1
},
{
    "category": "Toiletry",
    "bought": false,
    "id": "60b92fe97ae0934c8dfce127",
    "name": "Toothpaste",
    "price": 0,
    "quantity": 1
},
{
    "category": "Toiletry",
    "bought": false,
    "id": "60b92ffb7ae0934c8dfce128",
    "name": "Mouthwash",
    "price": 0,
    "quantity": 1
},
{
    "category": "Toiletry",
    "bought": false,
    "id": "60b931fa7ae0934c8dfce12d",
    "name": "Body Soap",
    "price": 0,
    "quantity": 1
},
{
    "category": "Fruit",
    "bought": false,
    "id": "60b9300c7ae0934c8dfce129",
    "name": "Banana",
    "price": 0,
    "quantity": 1
},
{
    "category": "Vegetable",
    "bought": false,
    "id": "60b930347ae0934c8dfce12a",
    "name": "Sombe",
    "price": 0,
    "quantity": 1
},

Query :

MyModel.updateMany(
    { _id: yourDocumentId },
    { $pull: { items: { id: { $in: itemIds } } } },
    { multi: true }
);

Note: ItemIds is an array of ObjectId. See below :

[
  '60ada26be8bdbf195887acc1',
  '60b930347ae0934c8dfce12a',
  '60b9300c7ae0934c8dfce129'
]

Using MongoDB $pull to delete documents within an Array

4 Answers4

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