Adding additional fields to an embedded document

Question

I make extensive use of embedded documents in my MongoDB database and I'm running into speed problems when trying to add additional data:

As an example I have a document that looks a bit like this:

    {
       "date" : <<the date>>
       "name" : "thisName"
       "basket": [
                   {
                     "stock": "IBM",
                     "quantity": 1000.0,
                     "profit"  : 10:0,
                   },
                   ...
                   {
                     "stock": "MSFT",
                     "quantity": 2000.0,
                     "profit"  : 30:0,
                   },

                 ]
}

What I want to do is to add 5 new fields in the embedded documents like this:

    {
       "date" : <<the date>>
       "name" : "thisName"
       "basket": [
                   {
                     "stock": "IBM",
                     "quantity": 1000.0,
                     "profit"  : 10:0,
                     "new_1"  : 10:0,
                     "new_2"  : 10:0,
                     "new_3"  : 10:0,
                     "new_4"  : 10:0,
                     "new_4"  : 10:0,
                     "new_5"  : 10:0
                   },
                   ...
                   {
                     "stock": "MSFT",
                     "quantity": 2000.0,
                     "profit"  : 30:0,
                     "new_1"  : 10:0,
                     "new_2"  : 10:0,
                     "new_3"  : 10:0,
                     "new_4"  : 10:0,
                     "new_4"  : 10:0,
                     "new_5"  : 10:0
                   },

                 ]
}

I started doing this using find().update_one() in a for loop, identifying each embedded document explicitly and using document explicitly using "$set". This approach works but it is very slow. If my collection was small I'm sure that this wouldn't matter but as it is it's huge (100's of millions of documents). It's probably so slow because the entire document has to be moved every time I add a set of fields. With that in mind I attempted to add the new fields to all the embedded documents in one go. I did this by leaving the find query empty and removing the positional $ from the "$set" command. A little like this (in pymongo):

bulk.find({"date": dates[i],
           "strategyId": strategyInfo[siOffset[l]][ID]
          }).update({
                     "$set": {
                          "basket.new_1": 0.0,
                          "basket.new_2": 0.0,
                          "basket.new_3": 0.0,
                          "basket.new_4": 0.0,
                          "basket.new_5": 0.0
                         }
                      })

This approach seems to throw an error cannot use the part (basket of basket.new_5) to traverse the element ({basket:......

Is anyone able to give some insight as to what I'm doing wrong? Is it even possible to do this?

possible duplicate of How to Update Multiple Array Elements in mongodb — Andriy Simonov
– Andriy Simonov, Commented Oct 25, 2016 at 11:19
I agree it's possibly an duplicate but MongoDB has changed significantly since 2011. — Richard B
– Richard B, Commented Oct 25, 2016 at 11:21

Vince Bowdren · Accepted Answer · 2016-10-25 15:42:02Z

1

You can use a recursive function like this.

First find all that data for update

db.collection('game_users').find(
    {"date": dates[i],"strategyId": strategyInfo[siOffset[l]][ID]}
).toArray(function(err, data) {
    var i=0;
    function data_Update(){
        if(i!=data.length){
            db.collection('game_users').update(
                {"date": dates[i],"strategyId": strategyInfo[siOffset[l]][ID]},
                { $set : {
                    "basket.new_1": 0.0,
                    "basket.new_2": 0.0,
                    "basket.new_3": 0.0,
                    "basket.new_4": 0.0,
                    "basket.new_5": 0.0
                    }
                },
                function(err, resp) {
                    i++;
                    data_Update();
                }
            );
        }
    }
}
);`

edited Oct 25, 2016 at 15:42

Vince Bowdren

9,2853 gold badges37 silver badges61 bronze badges

answered Oct 25, 2016 at 10:46

Jay Jariwala

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2 Comments

Richard B Over a year ago

It's not clear to me that this approach will be quicker than the one I'm using. Isn't this another way of executing a loop? and as such the server will move the entire document every time it updates one sub-document?

Jay Jariwala Over a year ago

When old user sign up in your app..at that time u check this field if not in user profile u can add...i thing without loop not possible....

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