Use of $isolated inhibits query by id runner selection

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    • Type: Bug
    • Resolution: Done
    • Priority: Major - P3
    • 2.5.5
    • Affects Version/s: None
    • Component/s: Querying
    • Fully Compatible
    • ALL
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      Run an _id query driven workload under 'perf top', and notice the IDHackRunner in the output. Re-run with $isolated, and note that the IDHackRunner goes away, and the QueryPlanner::plan function appears. Also, if you measure throughput, it is noticeably slower.

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      Run an _id query driven workload under 'perf top', and notice the IDHackRunner in the output. Re-run with $isolated, and note that the IDHackRunner goes away, and the QueryPlanner::plan function appears. Also, if you measure throughput, it is noticeably slower.
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      Normally, a query like

      { _id : 1 }

      will be routed to the "id hack" query runner. However, if the query is marked isolated with

      { _id : 1, $isolated : 1 }

      , then the query execution is routed through QueryPlanner::plan, rather than redirected to the id hack runner, which greatly reduces performance.

            Assignee:
            David Storch
            Reporter:
            Andrew Morrow (Inactive)
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              Created:
              Updated:
              Resolved: