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  1. Core Server
  2. SERVER-15152

When evaluating plans, some index candidates cause complete index scan

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • 2.6.4
    • 2.6.5, 2.7.7
    • Querying
    • None
    • ALL

    Description

      When running query during multiPlanRunner stage some combinations of values and data distribute can cause a fast query have a possible plan/index choice where full index scan (of a non-selective attribute) would be evaluated. Running explain(true) can show which index has unusually high nscanned.

      It seems during race-off the full scan is finished, causing some percentage of queries to be excessively slow.

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              david.storch@mongodb.com David Storch
              asya.kamsky@mongodb.com Asya Kamsky
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                Created:
                Updated:
                Resolved: