static void UpsertJunk(IMongoCollection <Junk> col, Junk junk)
        {
            var filterCondition = Builders <Junk> .Filter.Eq(j => j.RowId, junk.RowId);

            var updateCondition = Builders <Junk> .Update.Set(j => j.Data, junk.Data);

            col.UpdateOne(filterCondition, updateCondition, new UpdateOptions {
                IsUpsert = true
            });
        }
        static void InsertData(int start, int run = 5000)
        {
            var client   = new MongoClient("mongodb://localhost:27017");
            var database = client.GetDatabase("demo"); // no need to create it.
            var col      = database.GetCollection <Junk>("cur_data");

            var init = start * run;

            Console.WriteLine($"Inserting {init} through {init + run}.");
            for (var i = init; i < init + run; i++)
            {
                var junk = new Junk()
                {
                    RowId = i.ToString(),
                    Data  = RandomString(2048)
                };
                UpsertJunk(col, junk);
            }
            Console.WriteLine($"Finished inserting {init} through {init + run}.");
        }