Updating array within mongodb record with mongoose

Question

What is the best way to update a value within an array saved in a mongodb record? Currently, I'm trying it this way:

Record.find({ 'owner': owner}, {}, {sort: { date: -1 }}, function(err, record){
    if(!err){
        for (var i = 0; i < record[0].array.length; i++){
            record[0].array[i].score = 0;

            record[0].array[i].changed = true;

            record[0].save();
        }
    }
 });

And the schema looks like this:

var recordSchema = mongoose.Schema({
    owner: {type: String},
    date: {type: Date, default: Date.now},
    array: mongoose.Schema.Types.Mixed
});

Right now, I can see that the array updates, I get no error in saving, but when I query the database again, the array hasn't been updated.

I've tried it both inside and outside, the array is still not updated — alreadytaken
– alreadytaken, Commented Jul 25, 2013 at 18:45
I believe your query also should null where you have an empty object in its arguments. Mongoose docs — max
– max, Commented Jul 25, 2013 at 18:55

Peter Lyons · Accepted Answer · 2013-07-25 18:57:32Z

14

It would help if you explained your intent here as naming a property "array" conveys nothing about its purpose. I guess from your code you hope to go and set the score of each item there to zero. Note your save is currently being ignored because you can only save top-level mongoose documents, not nested documents.

Certain find-and-modify operations on arrays can be done with a single database command using the Array Update Operators like $push, $addToSet, etc. However I don't see any operators that can directly make your desired change in a single operation. Thus I think you need to find your record, alter the array date, and save it. (Note findOne is a convenience function you can use if you only care about the first match, which seems to be the case for you).

Record.findOne({ 'owner': owner}, {}, {sort: { date: -1 }}, function(err, record){
    if (err) {
       //don't just ignore this, log or bubble forward via callbacks
       return;
    }
    if (!record) {
        //Record not found, log or send 404 or whatever
        return;
    }
    record.array.forEach(function (item) {
        item.score = 0;
        item.changed = true;
    });
    //Now, mongoose can't automatically detect that you've changed the contents of 
    //record.array, so tell it
    //see http://mongoosejs.com/docs/api.html#document_Document-markModified
    record.markModified('array');
    record.save();        
 });

answered Jul 25, 2013 at 18:57

Peter Lyons

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2 Comments

alreadytaken Over a year ago

It worked! The reason why I simply named the property 'array' was to simplify the question. I've also changed it to findOne, thanks for that suggestion. Would changing from having the array be of type mongoose.Schema.Types.Mixed to a subdocument mongoosejs.com/docs/subdocs.html make it easier to update that information?

Peter Lyons Over a year ago

I don't think there's any schema that makes this a 1-command operation. You could just store the "array" docs in a totally separate collection with fields: score, record_id, changed, order properties, in which case you could reset them all at once with a multi-update. However, you lose the nice ability to manage order in the array. So it depends on whether the order in the array is important to your application and whether this kind of bulk reset is a common case or an edge case vs. needing to load all that data for a read operation.

Ron Wertlen · Accepted Answer · 2014-04-03 09:13:03Z

3

If you have a mongoose object of a document, you can of course update the array as in the question, with the following Caveat.

This is in fact a mongoose gotcha. Mongoose cannot track changes in the array of mixed, one has to use markModified:

doc.mixed.type = 'changed';
doc.markModified('mixed.type');
doc.save() // changes to mixed.type are now persisted

answered Apr 3, 2014 at 9:13

Ron Wertlen

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