Find index usage accross shards and display non used ones

index_delete_cadidates.js

databases  = db.adminCommand( { listDatabases: 1 } ).databases;
var deleteCandidates = []
databases.forEach(
	function(database){
		if ((database.name != "admin") && (database.name != "config") && (database.name != "test")){
			print ("Connecting to: " + database.name);
			conn = new Mongo();
			db = conn.getDB(database.name);
			db.getCollectionNames().forEach(function(collection){
				var indexUsageCounter = {};

				print("Checking collection: " + collection);
				indexStatsCursor = db.getCollection(collection).aggregate([{$indexStats:{}}]);
				mappedStats = indexStatsCursor.map( function(stat) { return { name: stat.name,  ops: stat.accesses.ops } ; } );
				mappedStats.forEach(function(stat){
					if (indexUsageCounter[stat.name] == undefined) {
						indexUsageCounter[stat.name] = stat.ops;
					} else {
						indexUsageCounter[stat.name] = indexUsageCounter[stat.name] + stat.ops;
					}
				});
				print(tojson(indexUsageCounter));
				var items = Object.keys(indexUsageCounter).map(function(key) {return [key, indexUsageCounter[key]];});
				items.forEach(function(usage){
					if(usage[1] == 0){
						print(usage);
						deleteCandidates.push(database.name + '.' + collection + '.' + usage[0]);
					}
				});
			});
		}
	}
);
print(tojson(deleteCandidates));