findOneAndUpdate causing duplication problem

Question

I am having a problem in findOneAndUpdate in mongoose. The case is that i am updating a document by finding it. The query is as follows:

UserModel.findOneAndUpdate({
individualId: 'some id'
}, {
$push: {
supporterOf: 'some string'
}
})

The 'supporterOf' is the ref of UserModel and its type is 'ObjectId'.

The issue i am facing here is that, 'some string' is being pushed twice under 'supporterOf' in the document.

Can anyone tell me that how to push an array element inside the document?

Answer 1

I have recently encountered the same problem. However, I managed to overcome this issue by some other logics (details given below) but couldn't understand the reason behind that why findOneAndUpdate inserting duplicate entries in mongodb.

You can overcome this problem by following logic.

Use findOne or findById instead of findOneAndUpdate to search the document in your collection and then manually update your document and run save().

You can have better idea with this code snippet

return new Promise(function (resolve, reject) {
    Model.findOne({
            someCondition...
        }, function (err, item) {
            if (err) {
                reject(err);
            } else {
                item.someArray.push({
                    someKeyValue...
                });
                item.save().then((result) => {
                    resolve(result)
                }).catch((err) => {
                    reject(err)
                });
            }
        }).catch((err) => {
            reject(err)
        });
   });

This will not insert duplicate item. However, if you come to know the reasoning behind duplication, must do update this thread.