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  1. Documentation
  2. DOCS-2743

Running explain no longer causes the query planner cache to be dropped

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    • Icon: Task Task
    • Resolution: Done
    • Icon: Major - P3 Major - P3
    • v1.3.2
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    Description

      Up until 2.5.5, when a user ran explain on a query, it would have the side effect of dropping the query plan cache for that query "shape."

      In 2.5.5+ this behavior no longer holds true and the full set of plans which are considered for the query are pulled from the queryPlanCache itself.

      The only direct user-triggered way of dropping the cached plan for a query is by using the QueryPlanCache manipulation methods directly.

      I'm not sure if this is mentioned anywhere in our documentation or whether this should be documented specifically, but it is a known behavior pre 2.5.5 and this is a backwards breaking change for users who depended on this behavior.

      See: SERVER-7468

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            kay.kim@mongodb.com Kay Kim (Inactive)
            dan@mongodb.com Daniel Pasette (Inactive)
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            Dates

              Created:
              Updated:
              Resolved:
              9 years, 50 weeks ago