MongoDB .local San Francisco 2020: Tips and Tricks++ for Querying and Indexing MongoDB

2. Tips and Tricks++ Querying For Indexing Ben Perlmutter Senior Solution Architect

3. Ben Perlmutter Senior Solution Architect

4. Ben Perlmutter Senior Solution Architect I identified slow queries. What index do I make?

5. Roadmap E-S-R Overview Guidelines: • Eà R • Eà S • Sà R E-S-R Considerations Operator Type Checks Consecutive Index Keys Exceptions?

7. Equality Sort Range "Rule"

8. E-S-R Have you thought about the order of the fields in a compound index?

9. E-S-R Have you thought about the order of the fields in a compound index? Does it really matter?

10. E-S-R Have you thought about the order of the fields in a compound index? 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. Definitions Equality Fields An exact match on a single value. For example: • {x:123} • {x:{$eq:123}} • {"x.y":123} Bounds: "[123.0, 123.0]"

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

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

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

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})

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"]" ] } gamertag db.games.createIndex({score:1, gamertag:1})

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})

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

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

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})

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})

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})

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

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

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

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

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

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

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

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

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

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

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

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

61. 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})

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

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}} ) R E R E Range after Equality

72. db.games.find( {gamertag: "Ace", score: {$gt: 9000}} ) R E R E Range after Equality Should range come after sort too?

73. R E R E Range after Equality Should range come after sort too? db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})

74. R E R E Range db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1})

75. 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})

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})

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

78. 100 15,000 50,000 99,999 Ace Bob Cali Ace * db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1}) Range {} {} {} {}{1}{2} {3} gamertag score db.games.createIndex({ …, score:1, gamertag:1})

79. 100 15,000 50,000 99,999 Ace Bob Cali 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})

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. 100 15,000 50,000 99,999 Ace Bob Cali Ace * {} {2} {3} {1} db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1}) Range

92. db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1}) Range * Ace Bob Cali Ace 100 15,000 50,00099,999 {} {1} {2} {3}

93. * 100 15,000 50,00099,999 Ace Bob Cali db.games.find({*, score: {$gt: 9000}}).sort({gamertag: 1}) Range {} {1} {3} score gamertag "indexBounds" : { *, "gamertag" : [ "[MinKey, MaxKey]" ] "score" : [ "(9000.0, inf.0]" ] } db.games.createIndex({ …, gamertag:1, score:1}) {2}

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

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

113. 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

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

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

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

123. 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! raincarry 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 Since the regex is left anchored, can’t we skip the middle tree?

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

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

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

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

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

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

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

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

146. Operator Type Check - $in .find({field:{$in:[1,3]}}) .sort({sortField:1}) ? 1 2 3 C G B F A D db.coll.createIndex({field:1, sortField:1})

147. Operator Type Check - $in .find({field:{$in:[1,3]}}).sort({sortField:1}) ? 1 2 3 C G B F A D db.coll.createIndex({field:1, sortField:1})

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

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

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

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

158. BS S M Operator Type Check - $in

159. Operator Type Check – Cheat Sheet $eq - EQUALITY $gte - RANGE $ne - RANGE $nin - RANGE $regex – RANGE $in • If alone – a series of EQUALITY matches • If combined – possibly a RANGE

161. 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” })

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

163. 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})

164. 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})

165. 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})

171. 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})

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

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

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

180. 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})

181. 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})

182. 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 {} {} {} db.games.createIndex({gamertag:1, score:1, date:1}) "indexBounds" : { "gamertag" : [ "["Ace", "Ace"]" ], "score" : [ "[MinKey, MaxKey]" ], "date" : [ "[2019.0, inf.0]" ] } {1} {2}

196. 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 {} {} {} "executionStats" : { "nReturned" : 2, "executionTimeMillis" : 23, "totalKeysExamined" : 9001, "totalDocsExamined" : 2, db.games.createIndex({gamertag:1, score:1, date:1}) {1} {2}

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

198. 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

199. 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]" ] }

204. Exceptionsdb.games .find({gamertag:"Ace", date:{$gte:2019}}) .sort({score:1}) Ace … … 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, db.games.createIndex({gamertag:1, date:1}) "indexBounds" : { "gamertag" : [ "["Ace", "Ace"]" ], "date" : [ "[2019.0, inf.0]" ] }

205. Exceptions ……… … BS S R E R E

206. Summary

207. 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

208. Thank You!

MongoDB .local San Francisco 2020: Tips and Tricks++ for Querying and Indexing MongoDB

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