MongoDB query cheetsheet

mongoDB.js

//update test collection
db.test.update({foo: "bar"}, {$set: {test: "success!"}}, {multi: true})

//Find duplicate records by key_name in MongoDB
db.collection.aggregate(
    {"$group" : { "_id": "$key_name", "count": { "$sum": 1 } } },
    {"$match": {"_id" :{ "$ne" : null } , "count" : {"$gt": 1} } }, 
    {"$project": {"key_name" : "$_id", "_id" : 0} }
)

//remove duplicate documnets by key_name (Index your key_name before running this to increase speed)
db.collection.find({}, {key_name:1}).sort({_id:1}).forEach(function(doc){
    db.collection.remove({_id:{$gt:doc._id}, key_name:doc.key_name});
})