Is there any easy way to copy collection data into another in MEAN app?

Question

I'm currently implementing admin dashboard of online shopping app.I want to implement method to perform user deletion and store that deleted user data temporally on another collection.

(Copy_userdata->Save it on another collection -> delete original data)

As an example my users data currently available in collection called users, and after deleting that user particular user's data must be available in another collection, lets say deleted_users collection. Are there any easy way to do that? thanks!

Your DB instance are same but only collection will be different? Also what have you tried so far? — Sohan, Jan 10 '20 at 10:10
Thanks for replying. Yes i want perform on same db. only collection will be deference. I have no idea about what to do. — Ransaka Ravihara, Jan 10 '20 at 10:14
@Sohan db version v4.0.10 git version: c389e7f69f637f7a1ac3cc9fae843b635f20b766 — Ransaka Ravihara, Jan 10 '20 at 10:31
You can use aggregate function and that will be the most efficient function. Once you copy the data next step would be deleting or dropping original collection — Sohan, Jan 10 '20 at 10:35
In below function look at the aggregation function and query — Sohan, Jan 10 '20 at 10:57

score 3 · Accepted Answer · answered Jan 10 '20 at 10:56

You will be modify some of the code but this is the basic logic,

Use aggregation for copy collections over Refer here for aggregate function using mongo client

So the function looks like this

public aggregation(collectionName: string, pipelines: Object[]): Promise<Array<any>>
    {
        return new Promise((resolve, reject) =>
        {
        let cursor: mongodb.AggregationCursor<any> = null;

             //Here you will use getCollection method on your own to fetch the collection
            this.getCollection(collectionName)
                .then((collection: mongodb.Collection) =>
                {
                    cursor = collection.aggregate(pipelines);

                    return cursor.toArray();
                })
                .then((result: Array<any>) =>
                {
                    return resolve(result);
                })
                .catch((error: any) =>
                { 
                    //error//
                });

    }

    public dropCollection(collectionName: string): Promise<any>
    {
        return new Promise((resolve, reject) =>
        {

           this.getCollection(collectionName)
                .then((collection: mongodb.Collection) =>
                {
                    collection.drop((err: Error, result: any) =>
                    {

                        if (err)
                        {
                            return reject(DataDropError);
                        }

                        return resolve(result);
                    });
                })
                .catch(reject);
        });
    }

     public async backupAndDrop()
    {
        const Object = [ { $match: {} }, { $out: "DeletedCollection" } ];

        try
        {
            await this.aggregationPipeline("originalCollection", Object);
            await  this.dropCollection("originalCollection");

        }
        catch (e)
        {
            throw e;
        }

    }

Also try to run this on your mongo shell:

db.originalCollection.aggregate([ { $match: {} }, { $out: "Backup" } ])

score 0 · Answer 2 · answered Jan 10 '20 at 10:14

0

Why don't you add a flag like isDeleted which is false by default and then make it true when the user is deleted?

answered Jan 10 '20 at 10:14

Niraj Patel

810
8
15

Thanks.yes, I also thought about it, but problem is if i add flag i also need to change my other codes too. – Ransaka Ravihara Jan 10 '20 at 10:20

score 0 · Answer 3 · answered Jan 10 '20 at 10:20

0

You can do something like this...

    Client.connect(connection_string, function(err, db) {
       if(err){
           console.log(err);
       }
       else{
           db.collection(CollectionA).find().forEach(function(d){ db.collection(CollectionB).insert(d); });
        }

Try out if it works.

This can help too: How to properly reuse connection to Mongodb across NodeJs application and modules

answered Jan 10 '20 at 10:20

Thanny

564
5
9

This will consume memory and it will be slow when you have millions of records in memory – Sohan Jan 10 '20 at 10:59

score 0 · Answer 4 · answered Jan 10 '20 at 10:46

You can first find the record to be deleted and do a create with that data to the new collection and then delete the record.

db.collection(CollectionA).findOne({userIdTODelete}, function(err, res){ 
         db.collection(CollectionB).insertOne(res, function() { 
            db.collection(CollectionA).deleteOne({userIdTODelete}); 
    }) 
});

Is there any easy way to copy collection data into another in MEAN app?

4 Answers4