Do all your queries use proper indexes? Really? A real life experience: In this talk I will reveal what might happen to your system if your queries do not use indexes and how to avoid this situation. I will show you different "built-in" possibilities to prevent missing indexes, and why they did not work for us! To solve the indexing issues we encountered at our company, I created a tool called "Mongo Query Inspector", which will be the main focus in this talk.

10. Investigation

12. 1

14. 2

15. 3
It is not cool when queries do not use indexes

17. 1

19. 2
notablescan

21. Regression tests will fail on
all CI environments due to
missing index exceptions

22. notablescan can
only be set on
the mongod
process
Integration and
acceptance tests
fail due to missing
indexes in test DBs

23. 3
ENABLE
PROFILING

24. Set profiling level to 1
in order to log all
queries that run longer
than 100ms

25. If there is
no traffic,
queries without index
only need 2ms

26. 4
explain()

27. We could use the
explain()
command to analyze
Queries

28. query

30. A TOOL THAT:
inspects
executed
queries for
missing
indexes
logs queries that did
not use an index
___is written
in node.js

31. A TOOL THAT:
inspects
executed
queries for
missing
indexes
logs queries that did
not use an index
___is written
in node.js

32. A TOOL THAT:
inspects
executed
queries for
missing
indexes
Logs queries that did
not use an index
is written
in node.js

34. Application
execute queries
MongoDB
collect profiling data (profiling level: 2)
system.profile
read profiling data
Mongo
Query
Inspector

35. Application
execute queries
MongoDB
collect profiling data (profiling level: 2)
system.profile
read profiling data
Mongo
Query
Inspector

36. Application
execute queries
MongoDB
collect profiling data (profiling level: 2)
system.profile
read profiling data
Mongo
Query
Inspector

37. Query
run explain on query
Explain
result
analyze
explain result
Index missing?
log query
and fields to
apply index
on
YES
NO
Keep
calm and
carry on!

38. Query
run explain on query
Explain
result
analyze
explain result
Index missing?
log query
and fields to
apply index
on
YES
NO
keep
calm and
carry on!

42. Integrate the Inspector in your build pipeline…

45. SUMMARY:
Problem
approach
notablescan
profiling
explain()
Solution

46. SUMMARY:
Problem
approach
notablescan
profiling
explain()
Solution

47. SUMMARY:
Problem
approach
notablescan
profiling
explain()
Solution

48. https://github.com/meckert/mongoQueryInspector

49. detect
obsolete
indexes
Index
optimization
contributers