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  1. Moodle
  2. MDL-52801

healthcheck hangs up on a certain set of data: introduce new DML aggregation method for concatenation

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      problem_000013 class from admin/tool/health/index.php sends an unoptimal database query which makes N*M scans in the database (N,M - number of rows in

      {question}

      ,

      {question_multianswer}

      accordingly) which is very time-consuming process.

      TO REPRODUCE:
      create 500k records in both tables and try to run
      /admin/tool/health/index.php script

      WHAT EXPECTED:
      linear complexity at least. Execution time < 30 seconds

      WHAT HAPPENED:
      N^2 complexity. Execution time > 900 seconds

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              Unassigned Unassigned
              baleevskii Grigory Baleevskiy
              Andrew Lyons, Huong Nguyen, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze, Andrew Lyons, Huong Nguyen, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze, Safat Shahin, Tim Hunt, Andrew Lyons, Huong Nguyen, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze
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                Created:
                Updated: