MongoDB Unable to delete item from array

Question

I've been at this problem for the whole day and I just can't seem to grasp what is the problem with $pull method in MongoDB, I am trying to remove an item from my shopping cart and I always get this:

WriteResult({ "nMatched" : 0, "nUpserted" : 0, "nModified" : 0 })

I want to remove item from my array 'products' in my schema with title of BTC

My 'carts' collection data in MongoDB:

{
    "userId": {
        "$oid": "5f940f8876ad3e073a2e1e8b"
    },
    "__v": 0,
    "products": [{
        "_id": {
            "$oid": "5fc6888b1e10cd1b01382ec2"
        },
        "title": "BTC",
        "price": 10000,
        "amount": 6
    }],
    "totalPrice": 60000
}

My past 2 attempts:

db.carts.update({},
    { $pull: { "products": { title: 'BTC'} } } )
db.carts.update({ _id : '5fc6888b42d86bad7dafa319'},
    { $pull: { "products": { title: 'BTC'} } } )

Why don't I even get nMatched ?

Are you connected to the same database? Try use <db-name>

Wernfried Domscheit
– Wernfried Domscheit

2020-12-01 19:02:48 +00:00
Commented Dec 1, 2020 at 19:02 — Wernfried Domscheit
– Wernfried Domscheit, Commented Dec 1, 2020 at 19:02
Yes I am connected to the database

Johnn
– Johnn

2020-12-01 19:08:02 +00:00
Commented Dec 1, 2020 at 19:08 — Johnn
– Johnn, Commented Dec 1, 2020 at 19:08
Does this help? stackoverflow.com/a/62010213/2282634

Joe
– Joe

2020-12-01 19:31:03 +00:00
Commented Dec 1, 2020 at 19:31 — Joe
– Joe, Commented Dec 1, 2020 at 19:31

score 1 · Accepted Answer · 2020-12-01 20:02:00Z

1

Think the problem is _id is not a string

ObjectId = require('mongodb').ObjectID;

const id = new ObjectId("idHere")
db.carts.update(
    { _id : id },
    {$pull:{ "products":{ title:'BTC' } }} 
)

And the first example won't match because it's looking for an exact match.

you can experiment here

edited Dec 1, 2020 at 20:02

answered Dec 1, 2020 at 19:51

user12582392

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4 Comments

Johnn Over a year ago

Thank you very much, problem was that it wasn't ObjectId. Question about that, should I use ObjectId's usually or should I stick to custom String ids ?

user12582392 Over a year ago

As long as _id are produced by MongoDB i think the only way is to use ObjectID. You're welcome @Frskn

user12582392 Over a year ago

Also, you could check mongoose, it has functions prepackaged for that (and I believe mongodb driver hasnt). For example mongoosejs.com/docs/api.html#model_Model.findById (there is findByIdAndUpdate too!) @Frskn

Johnn Over a year ago

I am using it already, thank you, I test first on terminal before testing further in express

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