Calling explain & hint in node.js

explain_hint_in_node.js

// Hint sample

var MongoClient = require('mongodb').MongoClient;

function query_hint_helper(db, query, hint, close_db){
	var cursor = db.collection('bar').find(query, {}, hint);

	// Explain the query
	cursor.explain(function(err, explain_output){
		if (err) throw err;

		console.log('Hint output: ');
		console.dir(explain_output);

		if (close_db) return db.close;
	});	
}

MongoClient.connect('mongodb://localhost:27017/foo', function(err, db){
	if (err) throw err;

	var query = {'a':50, 'b':50, 'c':50};

	// Make a query but returns cursor. Also, hint the query to NOT using any indexes
	query_hint_helper(db, query, {'hint': {'$natural': 1}});

	// Let's spawn another cursor to do same query but with the hint that point to an existing index
	query_hint_helper(db, query, {'hint': {'a': 1}}, true);

});

explain_in_node.js

// Explain sample

var MongoClient = require('mongodb').MongoClient;

MongoClient.connect('mongodb://localhost:27017/foo', function(err, db){
	if (err) throw err;

	// Make a query but returns cursor
	var cursor = db.collection('bar').find({'a':50, 'b':50, 'c':50});

	// Explain the query
	cursor.explain(function(err, explain_output){
		if (err) throw err;

		console.dir(explain_output);

		return db.close();
	});	
});