Reduce multi-planning cost for non selective index scan plans

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    • Type: Task
    • Resolution: Fixed
    • Priority: Major - P3
    • 8.2.0-rc0
    • Affects Version/s: None
    • Component/s: None
    • Query Optimization
    • Fully Compatible
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      The issue described in SERVER-31078 and in the corresponding section of the Design Doc.

      In short, the solution implemented here is to limit total multiplanning "works" to no more than 2x the size of the collection, regardless of the number of candidate plans (under default server parameter values). This reduces the cost of multiplanning in the worst case scenario by about 10x. Before this change, in the worst case scenario (64 relevant indexes) the max "works" would be 19.2x the collection size under default parameter values (0.3x the collection size times 64 plan candidates).

      We need to:

      1. Reproduce the issue in a test workload

      2. Implement the fix described in the Design

      3. Verify that the issue is mitigated using the test workload

            Assignee:
            Henri Nikku
            Reporter:
            Alexander Ignatyev
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              Created:
              Updated:
              Resolved: