[SERVER-4309] automatically select an index to sort by for MR to increase performance Created: 17/Nov/11  Updated: 06/Dec/22

Status: Backlog
Project: Core Server
Component/s: MapReduce
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Antoine Girbal Assignee: Backlog - Query Optimization
Resolution: Unresolved Votes: 1
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Query Optimization
Participants:

 Description   

In many cases of MR, people emit 1 key and usually have an index on it.
But few people actually think about sorting, even though it can greatly improve performance.
We can try to automate this for simple cases:

  • run the map once on a single doc with a special emit method
  • if emitted value is simple, try to match corresponding field in the doc
  • if the field has an index, use that index, otherwise maybe log a line advising index

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