CODEWITHSUNDEEP
mongodb
dragonalvaro
dragonalvaro

Reputation: 783

Mongo update array of string into array of embedded objects

I have some data stored in my MongoDB. The "tags" fields is actually an array of Strings, but we have to update our model to store more data with those tags

Current model document

{
    "id" : "59e4aefd74f12800019ba565",
    "title" : "This is a title",
    "tags" : [ 
        "59b02e6f6b28ce0001f8c0a8", 
        "59b031886b28ce0001f8c0af", 
        "59ba8c1a5047570001a3c078"
    ]
}

Desired model after update

{
    "id" : "59e4aefd74f12800019ba565",
    "title" : "This is a title",
    "tags" : [ 
        {
            "id" : "5a82ff1d889a15000103b115",
            "internalName" : "Día Mundial de la Television"
        }, 
        {
            "id" : "59ba8c1a5047570001a3c078",
            "internalName" : "menu"
        }, 
        {
            "id" : "5a26ac73d0fc2e00017f286e",
            "internalName" : "oid_asdf_asd"
        }
    ],


}

Now tags is a embedded object (forget about internalName field). How can I update the tag field without losing those data? I've tried with $rename, but it doesn't work well with arrays

db.test.update({}, {$rename: {'tags': 'tags2.id'}})

Upvotes: 1

Views: 159

Answers (1)

chridam
chridam

Reputation: 103435

Using the concepts from this very good answer, you could create a cursor from an aggregate operation that transforms the tags arrays by using the $map operator, iterate the cursor and update your collection using bulkWrite. The aggregate operation follows:

var cursor = db.test.aggregate([
    {
        "$project": {
            "tags": {
                "$map": {
                    "input": "$tags",
                    "as": "el",
                    "in": { 
                        "id": "$$el",
                        "internalName": { "$literal": "temp string" }
                    }
                }
            }
        }
    }
]);

And running the bulk update:

var bulkUpdateOps = [];

cursor.forEach(doc => {
    const { _id, tags } = doc;
    bulkUpdateOps.push({
        "updateOne": {
           "filter": { _id },
           "update": { "$set": { tags } },
           "upsert": true
        }
    });

    if (bulkUpdateOps.length === 1000) {
        db.test.bulkWrite(bulkUpdateOps);  
        bulkUpdateOps = [];                 
    }
}); 

if (bulkUpdateOps.length > 0) {
    db.test.bulkWrite(bulkUpdateOps);
}

Upvotes: 1

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