Query performance can either be a constant headache or the unsung hero of an application. MongoDB provides extremely powerful querying capabilities when used properly. As a senior member of the support team I will share more common mistakes observed and some tips and tricks to avoiding them.

2. Tips and Tricks++
for Indexing MongoDB
Ronán Bohan
Principal Solutions Architect, EMEA
v 20190922

3. Introductions
{
name : “Ronán Bohan”,
role : “Principal Solutions Architect”
}

4. Introductions
I’ve identified some slow queries.
What indexes do I create?

5. Introductions
For that we’re going to look at
compound indexes and
the “E-S-R” rule

6. Roadmap
E-S-R Overview
Deep dive:
• Equality
• Sort
• Range
E-S-R Considerations
Operator Type Checks
Exceptions?

7. Equality Sort Range "Rule"

8. E-S-R
The ordering of index keys in a compound index is critically important.

9. E-S-R
The ordering of index keys in a compound index is critically important.
Sure, but does it really matter?

10. E-S-R
The ordering of index keys in a compound index is critically important.
E-S-R provides guidance that is useful in most cases:
• Equality first
• Sort next
• Range last

11. E-S-R
The ordering of index keys in a compound index is critically important.
E-S-R provides guidance that is useful in most cases:
• Equality first
• Sort next
• Range last
What is the difference between
Equality and Range?

12. Equality Fields
Definitions
An exact match on a single
value. For example:
• {x:123}
• {x:{$eq:123}}
• {"x.y":123}
Bounds:
"[123.0, 123.0]"
Sort Range Predicates

13. Definitions
Sort
The (entire) requested sort.
.sort({a:1})
.sort({a:1, b:-1})
An exact match on a single
value. For example:
• {x:123}
• {x:{$eq:123}}
• {"x.y":123}
Bounds:
"[123.0, 123.0]"
Bounds:
"[MinKey, MaxKey]"
Range PredicatesEquality Fields
"[MinKey, MaxKey]",
"[MinKey, MaxKey]"

14. Definitions
Sort Range Predicates
Any predicates that are not
exact matches. Some
operators include:
• {z:{$gt:9000}}
• {foo:{$lte:1000}}
The (entire) requested sort.
.sort({a:1})
.sort({a:1, b:-1})
An exact match on a single
value. For example:
• {x:123}
• {x:{$eq:123}}
• {"x.y":123}
Bounds:
"[123.0, 123.0]"
Bounds:
"[MinKey, MaxKey]",
"[MinKey, MaxKey]"
Bounds:
"(9000.0, inf.0]"
"[-inf.0, 1000]"
Equality Fields

15. Roadmap
E-S-R Overview
Deep dive:
• Equality
• Sort
• Range
E-S-R Considerations
Operator Type Checks
Exceptions?

16. Equality
Equality keys are placed first in any order
If present in the query shape,
equality fields should always form the prefix for the index.

17. Equality
Equality keys are placed first in any order
If present in the query shape,
equality fields should always form the prefix for the index.
Why?

18. Equality
Equality keys are placed first in any order
If present in the query shape,
equality fields should always form the prefix for the index.
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )

19. Equality
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
If present in the query shape,
equality fields should always form the prefix for the index.
Equality keys are placed first in any order

20. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
Equality
{gamertag: "Ace", score: 100}
{gamertag: "Ace", score: 99,999}
{gamertag: "Bob", score: 15,000}
{gamertag: "Bob", score: 50,000}

21. 99,999
{gamertag: "Bob", score: 15,000}{gamertag: "Ace", score: 100}
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {}
{}{}
100 15,000 50,000
Ace Bob Bob Ace
{gamertag: "Ace", score: 99,999} {gamertag: "Bob", score: 50,000}
Equality
db.games.createIndex({score:1, gamertag:1})
gamertag
score
ANTI-pattern index:

22. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
db.games.createIndex({score:1, gamertag:1})
gamertag
score
ANTI-pattern index:

23. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
db.games.createIndex({score:1, gamertag:1})
gamertag
score
ANTI-pattern index:

24. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

25. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

26. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

27. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

28. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

29. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

30. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

31. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

32. 100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
Equality
db.games.createIndex({gamertag:1, score:1})Recommended index:

33. Ace Bob Bob Ace
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
100 99,999 15,000 50,000
{} {} {} {}
Equality
db.games.createIndex({gamertag:1, score:1})
gamertag
score
Recommended index:

34. 100
Ace Bob
99,999 15,000 50,000
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"(9000.0, inf.0]"
],
}
db.games.createIndex({gamertag:1, score:1})
gamertag
score
Recommended index:

35. 100
Ace Bob
99,999 15,000 50,000
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"(9000.0, inf.0]"
],
}
gamertag
db.games.createIndex({gamertag:1, score:1})
score
Recommended index:

36. 100
Ace Bob
99,999 15,000 50,000
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"(9000.0, inf.0]"
],
}
gamertag
score
db.games.createIndex({gamertag:1, score:1})Recommended index:

37. 100
Ace Bob
99,999 15,000 50,000
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"(9000.0, inf.0]"
],
}
gamertag
score
db.games.createIndex({gamertag:1, score:1})Recommended index:

38. 100
Bob
99,999 15,000 50,000
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"(9000.0, inf.0]"
],
}
gamertag
score
Ace
db.games.createIndex({gamertag:1, score:1})Recommended index:

39. 100
Bob
99,999 15,000 50,000
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
{} {} {} {}
Equality
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"(9000.0, inf.0]"
],
}
gamertag
score
Ace
✓
db.games.createIndex({gamertag:1, score:1})Recommended index:

40. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
R
E R
E
Equality before Range
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}

41. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
R
E R
E
Equality before Range
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}
Hey! Don’t forget about your
demo!!

42. Roadmap
E-S-R Overview
Deep dive:
• Equality
• Sort
• Range
E-S-R Considerations
Operator Type Checks
Exceptions?

43. Sort fields are placed next
Placing sort predicates after sequential equality keys allows the index to:
- Provide a non-blocking sort.
- Minimize the amount of scanning required.
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort

44. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

45. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
{} {} {} {}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

46. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
{} {} {} {}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score

47. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
{} {} {} {}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score

48. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
{1} {} {} {2}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
gamertag
score

49. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Acegamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

50. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Acegamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

51. db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Sort
100 15,000 50,000 99,999
Ace Bob Bob Acegamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

52. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

53. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

54. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

55. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

56. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

57. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

58. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"score" : [
"[MinKey, MaxKey]"
],
"gamertag" : [
"["Ace", "Ace"]"
]
}
{1} {} {} {2}
✓✓
db.games.createIndex({score:1, gamertag:1})ANTI-pattern index:

59. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )

60. Sort
100 15,000 50,000 99,999
Ace Bob Bob Ace
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
db.games.createIndex({gamertag:1, score:1})Recommended index:

61. Sort
Ace Bob Bob Ace
100 99,999 15,000 50,000
{1} {2} {} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
db.games.createIndex({gamertag:1, score:1})
gamertag
score
Recommended index:

62. Sort
100
Ace Bob
99,999 15,000 50,000
{}{1} {2} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({gamertag:1, score:1})Recommended index:

63. Sort
100
Ace Bob
99,999 15,000 50,000
{}{1} {2} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({gamertag:1, score:1})Recommended index:

64. Sort
100
Ace Bob
99,999 15,000 50,000
{}{1} {2} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({gamertag:1, score:1})Recommended index:

65. Sort
100
Bob
99,999 15,000 50,000
{}{1} {2} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
]
}
Ace
db.games.createIndex({gamertag:1, score:1})Recommended index:

66. Sort
Bob
99,999 15,000 50,000
{}{1} {2} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
]
}
100
Ace
✓
db.games.createIndex({gamertag:1, score:1})Recommended index:

67. Sort
Bob
15,000 50,000
{}{1} {2} {}
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
gamertag
score
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
]
}
100 99,999
Ace
✓ ✓
db.games.createIndex({gamertag:1, score:1})Recommended index:

68. Sort after Equality
S
E S
E
db.games.find( {gamertag: "Ace"} ).sort( {score: 1} )
Don’t do this, it may require a full index scan
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}

69. Roadmap
E-S-R Overview
Deep dive:
• Equality
• Sort
• Range
E-S-R Considerations
Operator Type Checks
Exceptions?

70. Range fields are usually last
This allows them to :
Still participate in filtering the data
But does not force a blocking sort.
db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
Range

71. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
Range
Haven’t we seen this before?

72. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
R
E R
E
Range after Equality
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}

73. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} )
R
E R
E
Range
But should range come after
sort too?
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}

74. R
E R
E
Range
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
But should range come after
sort too?
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}

75. R
E R
E
Range
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
But should range come after
sort too?
Index: {gamertag:1, score:1}Index: {score:1, gamertag:1}
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

76. 100 15,000 50,000 99,999
Ace Bob Bob Ace
*
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

77. 100 15,000 50,000 99,999
Ace Bob Bob Ace
*
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

78. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

79. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {} {} {}{1}{2} {3}
gamertag
score
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

80. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

81. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

82. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

83. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

84. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
✓
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

85. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
✓
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

86. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
✓ ✓
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

87. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
✓ ✓
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

88. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
{} {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
gamertag
score
"indexBounds" : {
*,
"score" : [
"(9000.0, inf.0]"
],
"gamertag" : [
"[MinKey, MaxKey]"
]
}
✓ ✓ ✓
db.games.createIndex({…, score:1, gamertag:1})ANTI-pattern index:

89. {2} {3} {1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
Blocking SortBlocking Sort
BS

90. {2}
{3}{1}
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
BS

91. db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

92. 100 15,000 50,000 99,999
Ace Bob Cal Ace
*
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

93. db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
*
Ace Bob Cal Ace
100 15,000 50,00099,999
{} {1} {2} {3}
db.games.createIndex({…, gamertag:1, score:1})
score
gamertag
Recommended index:

94. *
100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

95. *
100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

96. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

97. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

98. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
✓
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

99. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
✓
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

100. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
✓ ✓
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

101. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
✓ ✓
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

102. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
✓ ✓ ✓
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

103. 100 15,000 50,00099,999
Ace Bob Cal
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range
{} {1} {3}
score
gamertag
"indexBounds" : {
*,
"gamertag" : [
"[MinKey, MaxKey]"
]
"score" : [
"(9000.0, inf.0]"
]
}
{2}
*
db.games.createIndex({…, gamertag:1, score:1})Recommended index:

104. BS
R S
R
S
db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})
Range after Sort
Index: {…, gamertag:1, score:1}
Index: {…, score:1, gamertag:1}

105. Roadmap
E-S-R Overview
Deep dive:
• Equality
• Sort
• Range
E-S-R Considerations
Operator Type Checks
Exceptions?

106. Operator Type Check
Some operators are simple
$eq: Equality
$gte: Range
Others are trickier

107. Operator Type Check - Inequality
Inequality Operators: E, S, or R?
• $ne:123
• $nin:[1,2]
Range!

108. Operator Type Check - Inequality
Inequality Operators: E, S, or R?
• $ne:123
• $nin:[1,2]
Range!
How do you know?

109. Operator Type Check - Inequality
Inequality Operators: E, S, or R?
• $ne:123
• $nin:[1,2]
Range!
"indexBounds" : {
"x" : [
"[MinKey, 123.0)",
"(123.0, MaxKey]"
]
}

110. Operator Type Check - Inequality
Range!
"indexBounds" : {
"x" : [
"[MinKey, 123.0)",
"(123.0, MaxKey]"
]
}
50 123 999

111. Operator Type Check - Inequality
Range!
"indexBounds" : {
"x" : [
"[MinKey, 123.0)",
"(123.0, MaxKey]"
]
}
50 123 999

112. Operator Type Check - Inequality
Range!
"indexBounds" : {
"x" : [
"[MinKey, 123.0)",
"(123.0, MaxKey]"
]
}
50 123 999

113. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!

114. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!

115. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
planecar racecar

116. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
planecar racecar

117. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
planecar racecar

118. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
p???ecar racecar

119. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
p???ecar racecar

120. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!

121. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
raincarry zebra

122. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
raincarry zebra

123. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
raincarry Carpool

124. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
raincarry Carpool

125. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
raincarry Carpool

126. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
raincarry Carpool
Since the regex is left
anchored, can’t we skip
the middle tree?

127. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
cArrycarry Carpool
Since the regex is left
anchored, can’t we skip
the middle tree?

128. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
cArrycarry Carpool
Since the regex is left
anchored, can’t we skip
the middle tree?

129. Operator Type Check - Regex
Regex Operators: E, S, or R?
• {str:/car/}
• {str:/^car/i}
Range!
cArrycarry Carpool

130. Operator Type Check - $in
$in filters: E, S, or R?
• {field:{$in:[1,3]}}
… it depends with respect to query shape
and key ordering
Alone: a series of Equality matches
Combined: possibly a Range

131. Operator Type Check - $in
.find({field1:{$in:[1,3]}})

132. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
db.coll.createIndex({field1:1, field2:1})

133. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
1 3

134. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
31

135. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
31

136. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
31

137. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
1 3
?

138. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
?
1 2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})

139. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
.sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
]
}
?
2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
1 3

140. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
.sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
],
"field2" : [
"[MinKey, MaxKey]"
]
}
?
2
C G B F A D
1 3
db.coll.createIndex({field1:1, field2:1})

141. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
.sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
],
"field2" : [
"[MinKey, MaxKey]"
]
}
?
2
C G B F A D
1 3
db.coll.createIndex({field1:1, field2:1})

142. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
.sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
],
"field2" : [
"[MinKey, MaxKey]"
]
}
?
2
C G B F A D
1 3
db.coll.createIndex({field1:1, field2:1})

143. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
.sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
],
"field2" : [
"[MinKey, MaxKey]"
]
}
?
2
C G B F A D
BS
1 3
db.coll.createIndex({field1:1, field2:1})

144. Operator Type Check - $in
.find({field1:{$in:[1,3]}})
.sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
"[3.0, 3.0]"
],
"field2" : [
"[MinKey, MaxKey]"
]
}
?
1 2 3
C G B F A D
BS
db.coll.createIndex({field1:1, field2:1})

145. Operator Type Check - $in
db.coll.createIndex({field1:1, field2:1})
.find({field1:{$in:[1,3]}}).sort({field2:1})

146. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
1

147. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})
1
?

148. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
1

149. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
1

150. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
"indexBounds" : {
"field1" : [
"[3.0, 3.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
?
1 2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})
?
1

151. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
"indexBounds" : {
"field1" : [
"[3.0, 3.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
1 2 3
C G B F A D
1 2 3
C G B F A D
db.coll.createIndex({field1:1, field2:1})
? ?

152. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
"indexBounds" : {
"field1" : [
"[3.0, 3.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
1 2
C G B F A D
db.coll.createIndex({field1:1, field2:1})
3
?
1
?

153. .find({field1:{$in:[1,3]}}).sort({field2:1})
"indexBounds" : {
"field1" : [
"[1.0, 1.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
"indexBounds" : {
"field1" : [
"[3.0, 3.0]",
],
"field2" : [
"[MinKey, MaxKey]"
]
}
Operator Type Check - $in
2 3
C G B F A D
1 2
C G B F A D
{2} {4} {1} {3}
Sort Merge
db.coll.createIndex({field1:1, field2:1})
?
1
?
3

154. BS
S M
Operator Type Check - $in

155. Roadmap
E-S-R Overview
Focus:
• Equality
• Sort
• Range
E-S-R Considerations
Operator Type Checks
Exceptions?

156. Exceptions
Is the E-S-R “rule” always optimal?
Nope.
Consider the following query:
db.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})

157. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
1 5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {} {1} {2}
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

158. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
1 5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

159. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
1 5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

160. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

161. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

162. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
5,000 9,0019,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 2
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

163. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
5,000 9,0019,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 2
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

164. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
9,0019,000
… …
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 2 5,000
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

165. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
9,0019,000
…
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 5,0002
…
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

166. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
9,001
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 5,0002 9,000
… …
Ace
db.games.createIndex({gamertag:1, score:1, date:1})Recommended index:

167. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
9,001
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 5,0002 9,000
… …
Ace
db.games.createIndex({gamertag:1, score:1, date:1})
✓
Recommended index:

168. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 5,000 9,0012 9,000
… …
Ace
db.games.createIndex({gamertag:1, score:1, date:1})
✓
Recommended index:

169. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"score" : [
"[MinKey, MaxKey]"
],
"date" : [
"[2019.0, inf.0]"
]
}
{1} {2}
1 5,000 9,0012 9,000
… …
Ace
db.games.createIndex({gamertag:1, score:1, date:1})
✓ ✓
Recommended index:

170. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
2001 2000 2015 2019 2019
gamertag
score
date
{} {} {}
"executionStats" : {
"nReturned" : 2,
"executionTimeMillis" : 23,
"totalKeysExamined" : 9001,
"totalDocsExamined" : 2,
{1} {2}
1 5,000 9,0012 9,000
… …
Ace
db.games.createIndex({gamertag:1, score:1, date:1})
✓ ✓
Recommended index:

171. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
1 5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019

172. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
1 5,000 9,0012 9,000
… …
2001 2000 2015 2019 2019
db.games.createIndex({gamertag:1, date:1})ANTI-pattern index:

173. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
2001 2000 2015 2019 2019
{score:2} {score:1} {score:5000} {score:9001} {score:9000}
… …
gamertag
date
db.games.createIndex({gamertag:1, date:1})ANTI-pattern index:

174. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
… …
2000 2001 2015 2019 2019
{score:2} {score:1} {score:5000} {score:9001} {score:9000}
gamertag
date
db.games.createIndex({gamertag:1, date:1})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[2019.0, inf.0]"
]
}
ANTI-pattern index:

175. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
Ace
… …
2000 2001 2015 2019 2019
{score:2} {score:1} {score:5000} {score:9001} {score:9000}
gamertag
date
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[2019.0, inf.0]"
]
}
db.games.createIndex({gamertag:1, date:1})ANTI-pattern index:

176. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
… …
2000 2001 2015 2019 2019
{score:2} {score:1} {score:5000} {score:9001} {score:9000}
gamertag
date
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[2019.0, inf.0]"
]
}Ace
db.games.createIndex({gamertag:1, date:1})ANTI-pattern index:

177. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
… …
2000 2001 2015 2019 2019
{score:2} {score:1} {score:5000} {score:9001} {score:9000}
gamertag
date
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[2019.0, inf.0]"
]
}Ace
db.games.createIndex({gamertag:1, date:1})
✓
ANTI-pattern index:

178. Exceptionsdb.games
.find({gamertag:"Ace", date:{$gte:2019}})
.sort({score:1})
… …
2000 2001 2015 2019 2019
{score:2} {score:1} {score:5000}
gamertag
date
{score:9001} {score:9000}
BS
"executionStats" : {
"nReturned" : 2,
"executionTimeMillis" : 0,
"totalKeysExamined" : 2,
"totalDocsExamined" : 2,
"executionStats" : {
"nReturned" : 2,
"executionTimeMillis" : 0,
"totalKeysExamined" : 2,
"totalDocsExamined" : 2,
"executionStages" : {
"stage" : "SORT",
"memUsage" : 154,
"memLimit" : 33554432,
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[2019.0, inf.0]"
]
}Ace
db.games.createIndex({gamertag:1, date:1})
✓ ✓
ANTI-pattern index:

179. Exceptions
……… …
BS
S
R
E
R
E
Index: {gamertag:1, date:1}
Index: {gamertag:1, score:1, date:1}

180. Summary

181. E-S-R Guidance
A good starting place applicable to
most use cases
Place keys in the following order:
Equality first
Sort next
Range last
Remember:
• Some operators may be range
instead of equality
• Having consecutive keys used in
the index is important
• Specifics about your data set may
need a different approach

182. Tips and Tricks++ for Indexing MongoDB
Ronan Bohan https://www.surveymonkey.com/r/KF8KX7B

183. Thank You!
And Thank You
from me too!

186. Appendix

187. Consecutive Index Keys
Given Indexes:
{gamertag:1, date:1, game:1}
{gamertag:1, game:1, date:1}
Which one is “better”?
It depends on the query shape(s)!
Consider the query:
.find({
gamertag: "Ace",
game: "Halo"
})

188. Consecutive Index Keys
.find({
gamertag:"Ace",
game: "Halo"
})

189. Consecutive Index Keys
.find({
gamertag:"Ace",
game: "Halo"
})
db.games.createIndex({gamertag:1, date:1, game:1})

190. Consecutive Index Keys
Ace
Mario Halo
2016 2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
db.games.createIndex({gamertag:1, date:1, game:1})

191. Consecutive Index Keys
Ace
Mario Halo
2016 2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})

192. Consecutive Index Keys
Ace
Mario Halo
2016 2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})

193. Consecutive Index Keys
Ace
Mario Halo
2016 2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})

194. Consecutive Index Keys
Mario Halo
2016 2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})
Ace

195. Consecutive Index Keys
Mario Halo
2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016
Ace

196. Consecutive Index Keys
Mario Halo
2017
Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016
Ace

197. Consecutive Index Keys
Mario Halo Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016 2017
Ace

198. Consecutive Index Keys
Mario Halo Mario Halo
2018 2019
.find({
gamertag:"Ace",
game: "Halo"
})
{} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016 2017
Ace
✓

199. Consecutive Index Keys
Mario Halo Mario Halo
2019
.find({
gamertag:"Ace",
game: "Halo"
})
{} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016 2017 2018
Ace
✓

200. Consecutive Index Keys
Mario Halo Mario Halo
2019
.find({
gamertag:"Ace",
game: "Halo"
})
{} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016 2017 2018
Ace
✓

201. "indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
Consecutive Index Keys
Mario Halo Mario Halo
.find({
gamertag:"Ace",
game: "Halo"
})
{} {} {} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016 2017 2018 2019
Ace
✓

202. Consecutive Index Keys
Mario Halo Mario Halo
.find({
gamertag:"Ace",
game: "Halo"
})
{} {}
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"date" : [
"[MinKey, MaxKey]"
],
"game" : [
"["Halo", "Halo"]"
]
}
{} {}
db.games.createIndex({gamertag:1, date:1, game:1})
2016 2017 2018 2019
Ace
✓ ✓

203. "indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
Consecutive Index Keys
.find({
gamertag:"Ace",
game: "Halo"
})
{} {} {} {}
"date" : [
"[MinKey, MaxKey]"
],
HaloMario Halo
2016 2017
Mario
2018 2019 "game" : [
"["Halo", "Halo"]"
]
}
db.games.createIndex({gamertag:1, game:1})
Ace
✓

204. 2016 2017Mario2018 2019Halo
Consecutive Index Keys
.find({
gamertag:"Ace",
game: "Halo"
})
],
"date" : [
"[MinKey, MaxKey]"
]
}
}
{}{} {}{}
db.games.createIndex({gamertag:1, game:1, date:1})
"indexBounds" : {
"gamertag" : [
"["Ace", "Ace"]"
],
"game" : [
"["Halo", "Halo"]"
]
Ace
✓✓

205. R
E
E E
E
E
E
Consecutive Index Keys
R
Look familiar? This is equality after range!