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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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        Issue Links

          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-14525 Perf regression in 2.6.2 caused by not caching plans that tie during plan ranking

          • Critical - P2 - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. SERVER-15528 Distinct queries can scan many index keys without yielding read lock

          • Major - P3 - Major loss of function.
          • Closed
          related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-14311 skipping of index keys is not accounted for in plan ranking by the index scan stage

          • Critical - P2 - Crashes, loss of data, severe memory leak.
          • Closed

          Activity

            People

              david.storch@mongodb.com David Storch
              asya.kamsky@mongodb.com Asya Kamsky
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              Dates

                Created:
                Updated:
                Resolved: