MongoDB: how to count number of keys in a document?

Question

Lets say a document is :

{

a: 1,
b: 1,
c: 2,
 ....
z: 2
}

How can I count the number of keys in such document?

Thank you

Answer 1

If you are in Mongo console, you can write javascript to do that.

doc = db.coll.findOne({}); nKeys =0; for( k in doc){nKeys ++;} print(nKeys);

This will still be considered "outside the mongo" though.