Identify last document from MongoDB find() result set

Question

I\'m trying to \'stream\' data from a node.js/MongoDB instance to the client using websockets. It is all working well.

But how to I identify the last document in t

Answer 1

Since mongodb objectId contatins creation date you can sort by id, descending and then use limit(1):

db.collection.find().sort( { _id : -1 } ).limit(1);

Note: i am not familiar with node.js at all, above command is mongo shell command and i suppose you can easy rewrite it to node.js.

Answer 2

Use sort and limit, if you want to use cursor :

var last = null;
var findCursor = collection.find({}).cursor();
findCursor.on("data", function(data) {
   last = data;
   ...
});
findCursor.on("end", function(data) {
   // last result in last
   ....
}); 

Answer 3

Say I have companies collection. Below snippet gives me last document in the collection.

db.companies.find({},{"_id":1}).skip(db.companies.find().count()-1);

Code cannot rely on _id as it may not be on a specific pattern always if it's a user defined value.