[SERVER-15226] Query plan cache should cache query plans that repeatedly tie with winning plan for a given shape Created: 11/Sep/14  Updated: 25/Jun/15  Resolved: 17/Feb/15

Status: Closed
Project: Core Server
Component/s: Querying
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: J Rassi Assignee: David Storch
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Duplicate
duplicates SERVER-15225 CachedPlanStage should execute for tr... Closed
Related
related to SERVER-13675 Plans with differing performance can ... Closed
Participants:

 Description   

For a query shape that has never been run before, it is not optimal to cache a plan if it ties with another, because not enough information is available to conclusively rule out either plan. However, for a query shape that generates two plans that are guaranteed to always tie, it is useless to run a trial for those two plans on every query. A better solution is to cache an arbitrary plan after it ties N times in a row with the winning plan.

Related: SERVER-15225.



 Comments   
Comment by David Storch [ 17/Feb/15 ]

This change will be included in work being done under SERVER-15225. Closing as a duplicate.

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