Question

For debugging purposes it would be great to be able to see just what you are getting back from the map method. Is this possible in ruby?

Answer 1

To do this in the Mongo shell, you can define you own debug version of the emit() function to print trace information.

function emit(k, v) {
    print("emit");
    print("  k:" + k + " v:" + tojson(v));
}

Check out Troubleshooting MapReduce in the MongoDB docs for more info.