Switch to using an Array instead of Object

[Glavin001]

• [x] Use Array instead of Object/Dictionary field

See http://stackoverflow.com/a/21924176/2578205

{
  timestamp_hour: ISODate("2013-10-10T23:00:00.000Z"),
  type: “memory_used”,
  values: [
    [ 999999, 999999, …, 1000000 ],
    [ 2000000, 2000000, …, 1000000 ],
    …,
    [ 1600000, 1200000, …, 1100000 ],
    [ 1300000, 1400000, …, 1500000 ]
  ]
}

[Glavin001]

• [x] store the count and total (and other stats) in a stats key:
• [x] store max and min

{
  timestamp_hour: ISODate("2013-10-10T23:00:00.000Z"),
  type: “memory_used”,
  values: [
    [ 999999, 999999, …, 1000000 ],
    [ 2000000, 2000000, …, 1000000 ],
    …,
    [ 1600000, 1200000, …, 1100000 ],
    [ 1300000, 1400000, …, 1500000 ]
  ],
  stats: [
    [ count, total, min, max], // Minute 0
    [ count, total, min, max], // Minute 1
    // ....
  ],
  count: 0,
  total: 0,
  min: 0,
  max: 0
}

[Glavin001]

Benchmarking

• 1000 sensors per second.

Before (using subdocument schema)

After (using array schema)

• Before implementing $max and $min

[Glavin001]

I notice that the min field is not getting set, because BSON comparison order puts null as less than a number. Instead of storing it in the order of [count, total, min, max], store it as [count, total, max, min] where min is empty by default, not null, such that on insert/default it is [0,0,0] for [count,total,max,min] and the $min update modifier will detect that the 3rd index is missing and initialize it with the minimum value.