MongoDB: Updating documents using data from the same document

user_457427 0
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I have a list of documents, each with lat and lon properties (among others).

{ 'lat': 1, 'lon': 2, someotherdata [...] } 
{ 'lat': 4, 'lon': 1, someotherdata [...] }
[...]

I want to modify it so that it looks like this:

{ 'coords': {'lat': 1, 'lon': 2}, someotherdata [...]} 
{ 'coords': {'lat': 4, 'lon': 1}, someotherdata [...]}
[...]

So far I've got this:

db.events.update({}, {$set : {'coords': {'lat': db.events.lat, 'lon': db.events.lon}}}, false, true)

But it treats the db.events.lat and db.events.lon as strings. How can I reference the document's properties?

Cheers.

mongodb
6 Answers

Neils answer. Just to let people know you cannot run this on a large database if you are lets say doing it remote shell like Robomongo. You will need to ssh into your actual server's mongo shell. Also you could also do this if you would rather do an Update.

db.Collection.find({***/ possible query /***}).toArray().forEach(
  function(obj){
    obj.item = obj.copiedItem;
    obj.otherItem = obj.copiedItem;
    obj.thirdItem = true;
    obj.fourthItem = "string";
    db.Collection.update({_id: obj._id}, obj);
  }
);
user_48078890
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