Mongo convert all numeric fields that are stored as string

Question

It looks like for a while now I\'ve been storing my decimals as strings. This is now a problem because I need to start using the aggregation framework to perform some calcul

Answer 1

Thanks for your response. I was unclear in my initial question in that I did not want to have to specify the fields to update to numbers, but rather walk each property and perform the check.

I have put together this little function to do the trick:

var cursor = db.results.find();
while (cursor.hasNext()) {
    var doc = cursor.next();
    for (key in doc) {
        if (key.match(/^metric_.*/i) && !isNaN(doc[key])) {
            doc[key] = parseFloat(doc[key]);
            db.results.update({ _id : doc._id }, doc );
        }
    }
}

Two things to note:

1. This only does the check and conversion to the first level of properties. It can be easily modified to go deeper, but this was all I needed at this time.
2. This function will blast your date values away!!! A javascript date is evaluated by isNaN as false, and therefore will be treated as a number. In my case, using parseFloat will actually set the value to isNaN. Again, a very easy fix for the onlooker, but I just wanted to provide that disclaimer.

Hope this helps someone else in my position.

Answer 2

Something like this should work from the mongo shell:

db.yourCollection.find({}).forEach(function(doc) { 
    if(isNaN(doc.xyz)) { 
        print('found string: ' + doc._id);
        db.yourCollection.update( 
           { _id: doc._id}, 
           { $set : { "xyz" : parseFloat(doc.xyz) } }
        )
    }
})

It loops through each document, uses isNaN as you suggested, then $sets the value to the parseFloat value for the current document.