MongoDB update multiple records of array [duplicate]

Answer 1

You cannot modify multiple array elements in a single update operation. Thus, you'll have to repeat the update in order to migrate documents which need multiple array elements to be modified. You can do this by iterating through each document in the collection, repeatedly applying an update with $elemMatch until the document has all of its relevant comments replaced, e.g.:

db.collection.find().forEach( function(doc) {
  do {
    db.collection.update({_id: doc._id,
                          comments:{$elemMatch:{user:"test",
                                                avatar:{$ne:"new_avatar.jpg"}}}},
                         {$set:{"comments.$.avatar":"new_avatar.jpg"}});
  } while (db.getPrevError().n != 0);
})

Note that if efficiency of this operation is a requirement for your application, you should normalize your schema such that the location of the user's avatar is stored in a single document, rather than in every comment.

Answer 2

If you know the indexes you want to update you can do this with no problems like this:

var update = { $set: {} };
for (var i = 0; i < indexesToUpdate.length; ++i) {
  update.$set[`comments.${indexesToUpdate[i]}. avatar`] = "new_avatar.jpg";
}
Comments.update({ "comments.user":"test" }, update, function(error) {
  // ...
});

• be aware that must of the IDE's will not accept the syntax but you can ignore it.

Answer 3

One solution could be creating a function to be used with a forEach and evaling it (so it runs quickly). Assuming your collection is "article", you could run the following:

var runUpdate = function(){
    db.article.find({"comments.user":"test").forEach( function(article) {
        for(var i in article.comments){
            article.comments[i].avatar = 'new_avatar.jpg';
        }
        db.article.save(article);
    });
};

db.eval(runUpdate);

Answer 4

It seems like you can do this:

db.yourCollection.update({"comments.user":"test"},{$set:{"comments.0.avatar": "new_avatar.jpg", "comments.1.avatar": "new_avatar.jpg", etc...})

So if you have a small known number of array elements, this might be a little easier to do. If you want something like "comments.*.avatar" - not sure how to do that. It is probably not that good that you have so much data duplication tho..