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  1. MariaDB Server
  2. MDEV-8056

Help needed for query plan change situations

        Details

        • Type: Task
        • Status: Open
        • Priority: Minor
        • Resolution: Unresolved
        • Fix Version/s: None
        • Component/s: None
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          Description

          Hello,

          we have mariaDB version 5.5.37 .

          We stumbled into an interesting situation:
          – at some point in time the query plan has changed making the server behave poorly
          – after a restart we noticed that the query plan was different behaving normally

          I've asked our DBA's to try and use this: https://mariadb.com/kb/en/mariadb/how-to-force-query-plans/ in order to have some sort of control.

          The query is fairly complex contains multiple joins and unions, this is the last entry in the explain result:
          22.
          id: NULL
          select_type: UNION RESULT
          table: <union2,3>
          type: ALL
          possible_keys: NULL
          key: NULL
          key_len: NULL
          ref: NULL
          rows: NULL
          Extra:

          I would like some help for:
          – getting info on why and how the optimizer made a choice (general optimizer info?)
          – what is your experience dictates for this situations ?

          Thank you .

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                  • Assignee:
                    Unassigned
                    Reporter:
                    cristian.nicoara82 Cristian Nicoara
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                    • Created:
                      Updated: