Don't get bitten by mungos (or mongos)

Don't get bitten by mungos

Order of properties matters in objects

{  "city": "SF",  "state": "CA"}

{  "state": "CA",  "city": "SF"}

Object queries

find({address: { city:"SF", state:"CA" }}) - badfind({ 'address.city': "SF", 'address.state': "CA" }) - better

Sort specifiers

 find().sort({ name: 1, _id: 1 })               !==  find().sort({ _id: 1, name: 1 })

Collection indexes

 collection.ensureIndex({ name: 1, address: 1 })                      !==                    collection.ensureIndex({ address: 1, name: 1 })

db.places:

{
  _id: "A",
  ratings: [5, 1, 3]
},
{
  _id: "B",
  ratings: [2, 4, 9]
},
{
  _id: "C",
  ratings: [1]
}

find().sort({ locations: 1 })

find({ locations: { $gt: 1 } }).sort({ locations: 1 })

locations: x x 2 3 4 5 9

_id: A C B A B A B

_id: A C B A B A B

locations: 1 1 2 3 4 5 9

{  _id: "A",  locations: [ [1, 2], [1, 0] ]},
{  _id: "B",  locations: [ [ 0, 0 ] ]}