MongoDB commands

//Copy the collection to prevent deleting data
db.nameCollection.copyTo('newNameCollection')

//See the collections in the database
db.getCollectionNames()

//See if exist duplicate data
db.orders.aggregate([
   { 
     $group: { 
        _id: { extOrderId: "$extOrderId" }, 
        uniqueIds: { $addToSet: "$_id" },
        count: { $sum: 1 } 
     }
   }, 
   { 
     $match: { 
        count: { $gt: 1 } 
     }
   }
])

//Remove duplicate data (Run this code until cur is empty)
var cur = db.orders.aggregate([{ $group: { _id: { extOrderId: "$extOrderId" }, uniqueIds: { $addToSet: "$_id" }, count: { $sum: 1 } } }, { $match: { count: { $gt: 1 } } }]);

while (cur.hasNext()) {
    var doc = cur.next();
    var index = 1;
    while (index < doc.uniqueIds.length) {
         db.orders.remove(doc.uniqueIds[index]);
        index = index + 1;
    }
}

//Compare the number of documents
db.orders14122015.distinct("extOrderId") 
db.orders.count()

//See the Indexes of one collection
db.orders.getIndexes()

//Create the Index
db.orders.createIndex( {"extOrderId":1},{unique:true})

//Drop temporal collections
db['tempcollection'].drop()