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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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      Description

      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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              Assignee:
              Unassigned
              Reporter:
              baleevskii Grigory Baleevskiy
              Participants:
              Component watchers:
              Andrew Nicols, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze, Andrew Nicols, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze, Tim Hunt, Andrew Nicols, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze
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                Dates

                Created:
                Updated: