Getting data from query result taking a long time

Working with Data
,
14

I know it’s weird. If you want to see it in “action” run the first part which I’ve stripped lots of stuff out of, to create 4000 records in a temp collection. Then run the second part against it. Try with the [0] commented out first. For me this runs in about 1/20th of a second. When uncommenting the [0] it takes about 8-10 seconds!

var toDate = new Date()
var epochTicks = 621355968000000000
var toTicks = ((toDate.getTime() * 10000) + epochTicks);
var count = 0
var shipNum = 621355968000000000

for (i = 0; i < 4000; i++) {
  count = count + 123456789
  shipNum = shipNum + 123456789
  db.tracking_temp.insert({
      "SecondEvent" : {
          "Code" : "1111"
      },
      "Ships" : {
          "Name" : "xyz",
          "Number" : NumberLong(shipNum)
      },
      "TrackTime" : [ 
          NumberLong(toTicks + count), 
          60
      ]
  })
}

…then run this. Doesn’t print or do anything but will show the jump in run duration.

var ships = db.tracking_temp.find({}, {_id:0, 'Ships.Number': 1}).toArray()
var shipsCount = ships.length

for (i = 0; i < shipsCount; i++) {
    var shipsNumber = ships[i].Ships.Number

    var minTick = db.tracking_temp.find({$and: [{'Ships.Number': shipsNumber}, {'SecondEvent.Code': "1111"}]}, 
    {_id: 0, 'TrackTime': 1}).limit(1)//[0]
    
    print()
}