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  1. Documentation
  2. DOCS-11962

Docs for SERVER-35981: Include hash of plan cache key in planCacheListShapes and planCacheListPlans



    • Task
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • 4.1.2
    • manual, Server
    • None



      Original Description


      The "queryHash" is now present in planCacheListPlans and planCacheListQueryShapes output. We may wish to document this in pages about these debug mechanisms? Right now it looks like we don't have detailed documentation about the output of these commands – I think we might want to keep it that way, in order to prevent users from depending too much on the particular format. These commands are mostly for use by TSEs or others who are diagnosing query performance issues.

      All queries with the same hash are considered the same "shape", and use the same plan cache entry. This may be useful for diagnosing issues around query performance. Please ask Storch for more details, and to review any proposed documentation changes.

      Note that https://jira.mongodb.org/browse/SERVER-23332 added this same 'queryHash' to the logs and system.profile, and https://jira.mongodb.org/browse/SERVER-36527 added it to explain output.



      Scope of changes (files that need work and how much)

      • reference/glossary  (when working on linked tickets, will touch core/query-plans)
      • 4.2
      • db.collection.getPlanCache().listQueryShapes()
      • db.collection.getPlanCache().getPlansByQuery(query[, projection, sort, collation]) - displays the cached plans for a query shape
      • db.collection.getPlanCache().clearPlansByQuery() 
      • planCacheListPlans
      • planCacheClear
      • planCacheListQueryShapes

      note: we're missing collation from the plancache methods/commands – but will do it as a separate ticket in order to backport just those through 3.4.

      Impact to other docs outside of this product

      MVP (work and date?)

      Resources (e.g. Scope Docs, Invision)


        Issue Links



              kay.kim@mongodb.com Kay Kim (Inactive)
              kay.kim@mongodb.com Kay Kim (Inactive)
              Kay Kim Kay Kim (Inactive)
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                3 years, 45 weeks, 1 day ago