Is it possible to cast in a MongoDB-Query?

Question

When I have two MongoDB documents like this...

db.test.insert( {"value" : "10123"} ); db.test.insert( {"value" : "160"} ); 

The result of a query like:

db.test.find({"value" :{$gt : "12"} }); 

is..

{ "_id" : ObjectId("4c6d1b92304326161b678b89"), "value" : "160" } 

It's obvious, that a string comparison is made, so that my first value is not returned. Is there any way to cast within the query?

Something like:

db.test.find({ (int) "value" :{$gt : 12} }); 

would be great. A query like

db.test.find({"value" :{$gt : 12} }); // without the quotes around "12" 

returns nothing.

Answer 1

You can use the following JavaScript expression:

db.test.find("this.value > 12") 

This uses JavaScript's automatic conversion from string to number.

Answer 2

I have a similar workaround, i find that if you can use the mongo shell, you can write an statement to do this in javascript, but capable of using indexes.

var myItems = [] var it = db.test.find({},{value:1}) while (it.hasNext()){  var item = it.next();  if(parseInt(item.value) > 12)   myItems.push(item); } 

If you want this to run faster than previus solution, you have to ensure the index on the value field.