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  1. MariaDB Server
  2. MDEV-17238

Document special thread IDs used in SHOW ENGINE INNODB STATUS output

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      SHOW ENGINE INNODB STATUS output seems to use special thread IDs in some sections of the output. For example, check out this line from the SEMAPHORES section:

      --Thread 139981888375552 has waited at lock0lock.cc line 7221 for 0.0000 seconds the semaphore:
      Mutex at 0x7f8859c88068 '&lock_sys->mutex', lock var 0
      Last time reserved by thread 18446744073709551615 in file not yet reserved line 0, waiters flag 0
      wait has ended
      

      This semaphore is supposedly held by a thread with ID 18446744073709551615. This thread ID is FFFFFFFFFFFFFFFF in hex. No threads with this ID are mentioned anywhere in the TRANSACTIONS section, so it does not appear to be a user thread. I would guess that this is a special identifier for some internal thread. If so, then we should document what thread this is referring to:

      https://mariadb.com/kb/en/library/show-engine-innodb-status/

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              Assignee:
              thiru Thirunarayanan Balathandayuthapani
              Reporter:
              GeoffMontee Geoff Montee
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                Created:
                Updated: