for an stream of pings, use the mongodb aggregation pipeline to find which urls do better in the morning than in the evening

find_daily_performance_increase.js

// The following is a function defined in the mongo shell
// use transfer       # switch to the transfer db
// t = transfer.test  # save the important collection off to this temp

// unfortunately this is stuck to only work on july 28, 2013
function show_daily_improvers(){
    return t.aggregate(
        {$match:{time:{$gte:ISODate("2013-07-28"),
                       $lt:ISODate("2013-07-29")}}
        },

        {$group:
            {_id:
                {url: "$url",
                 year: {$year:"$time"},
                 month: {$month:"$time"},
                 day: {$dayOfMonth:"$time"},
                 morning: {$cmp: [ISODate("2013-07-28T12"), "$time"]}},
             mean_ping: {$avg:"$duration"} }},


        {$project:{mean_ping: {$multiply: ["$_id.morning", "$mean_ping"]}}},

        {$group:
            {_id:{url: "$_id.url"},
             morning_performance:{$sum:"$mean_ping"}} },

        {$sort:{morning_performance:-1}},

        {$limit: 5}
    );
}