use variable as key name in mongo db with modifier

Question

I am trying to insert a bunch of arrays into mongoDB.

The data looks something like:

var places = {
    city: ['london', 'york', 'liverpool'],
    country: ['uk', 'france']
};

Each time I add an array, some of the entries could already be there, so I want to ensure there are no duplicates.

db.collection('places').ensureIndex({'city': 1}, {unique: true }, function(){ });
db.collection('places').ensureIndex({'country': 1}, {unique: true }, function(){ });

I then need to loop through the places object and add each item:

for(var key in places){

    db.collection('places').update({_id: 1}, { $addToSet: { key: { $each places[key] } } }, function(err, docs){
        if(err){
            console.log(err);
        }else{
            console.log('success');
        }
    });

}

Here I need key to be the actual keys: 'city', 'country'. Rather than literally being 'key'. But I cant see how this can be achieved with with the modifiers in place.

It is probably a stupid question, but why don't you add an empty array to every document so you don't have this problem? :) — Thomas Bormans
– Thomas Bormans, Commented Jan 25, 2015 at 11:55
Hmm, I am beginning to think I misunderstood your question. Do you want to make sure that the content of your city/country array is unique or do you want to make sure there is only one array of city/country in your document? — Thomas Bormans
– Thomas Bormans, Commented Jan 25, 2015 at 11:59
I want to ensure the content of the city/country array is unique. Sorry I should actually be specifying and id in the update to ensure im updating the same arrays. — wazzaday
– wazzaday, Commented Jan 25, 2015 at 12:02
You are indeed correct that you will need to specify your _id as your first selector. The rest of your code seems about right. Let me know if you are stil having problems. — Thomas Bormans
– Thomas Bormans, Commented Jan 25, 2015 at 12:06

JohnnyHK · Accepted Answer · 2015-01-25 14:59:00Z

2

You need to build up your $addToSet value programmatically:

for(var key in places){
    var addToSet = {};
    addToSet[key] = { $each: places[key] };
    db.collection('places').update({_id: 1}, {$addToSet: addToSet}, function(err, docs){
        if(err){
            console.log(err);
        }else{
            console.log('success');
        }
    });
}

But you can do this more efficiently by combining both updates into one:

var addToSet = {};
for(var key in places){
    addToSet[key] = { $each: places[key] };
}
db.collection('places').update({_id: 1}, {$addToSet: addToSet}, function(err, docs){
    if(err){
        console.log(err);
    }else{
        console.log('success');
    }
});

answered Jan 25, 2015 at 14:59

JohnnyHK

313k70 gold badges632 silver badges479 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

wazzaday Over a year ago

Awesome that it can be done in a single query. Thanks!

Collectives™ on Stack Overflow

use variable as key name in mongo db with modifier

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related