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  1. WiredTiger
  2. WT-7264

Creating a new configuration for search near that allows it to exit quickly when searching for prefixes

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • WT10.0.1, 4.4.7, 5.0.0-rc0
    • None
    • 8
    • Storage - Ra 2021-04-05, Storage - Ra 2021-04-19, Storage - Ra 2021-05-03
    • v4.4

    Description

      The issue was initially reported as an unusually long load phase in py-tpcc workloads. The issue appears intermittently as a few inserts in the load phase will get stuck for more than a few hours. Related PERF and HELP tickets have more information on the history of the issue.

      bruce.lucas has come up with a standalone reproducer, attached to the ticket.

      Issue:
      When inserting into a unique index, there is potential to get stuck repeatedly searching history store, ie calling __wt_hs_find_upd. We see a very high history store table reads missed statistic in these runs, which convey that these searches through history store are not returning anything. A callgraph that reflects this situation:

      Observed behaviour with the repro script:

      • Observed behaviour in 4.4 is that insert rate is erratic, and a couple of the threads typically seem to get stuck apparently indefinitely with a high rate of missed history store reads with stacks like the above.

      Acceptance criterion:

      • With the repro script: Expected behaviour (same as observed in 4.2) is that insert rate should be steady and each thread should complete at about the same time
      • py-tpcc load phase should not get stuck

      Attachments

        1. hs.png
          hs.png
          198 kB
        2. repro.sh
          1 kB
        3. 442.png
          442.png
          140 kB
        4. 441.png
          441.png
          114 kB
        5. image-2021-03-31-17-11-35-375.png
          image-2021-03-31-17-11-35-375.png
          29 kB
        6. image.png
          image.png
          198 kB

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              luke.pearson@mongodb.com Luke Pearson
              sulabh.mahajan@mongodb.com Sulabh Mahajan
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              Dates

                Created:
                Updated:
                Resolved: