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  1. MariaDB Server
  2. MDEV-21294

Name or content of metadata_lock_info table is wrong

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    Description

      Either the content or the name of the column THREAD_ID in table information_schema.metadata_lock_info is wrong. Correct name would be CONNECTION_ID or SESSION_ID because content is the connection_id and not the thread id.

      Proof:
      1. Provoke a MDL:
      1a) start transaction; select * from test where id < 10;
      1b) alter table test add column c9 int;

      2.)

      SELECT * FROM information_schema.metadata_lock_info;
      		 
      +-----------+-------------------------+---------------+----------------------+--------------+------------+
      		 
      | THREAD_ID | LOCK_MODE               | LOCK_DURATION | LOCK_TYPE            | TABLE_SCHEMA | TABLE_NAME |
      		 
      +-----------+-------------------------+---------------+----------------------+--------------+------------+
      		 
      |       413 | MDL_BACKUP_ALTER_COPY   | NULL          | Backup lock          |              |            |
      		 
      |       414 | MDL_SHARED_READ         | NULL          | Table metadata lock  | test         | test       |
      		 
      |       413 | MDL_SHARED_UPGRADABLE   | NULL          | Table metadata lock  | test         | test       |
      		 
      |       413 | MDL_INTENTION_EXCLUSIVE | NULL          | Schema metadata lock | test         |            |
      		 
      +-----------+-------------------------+---------------+----------------------+--------------+------------+
      		 
       
      		 
      SELECT *
      		 
          ->   FROM performance_schema.threads
      		 
          ->  WHERE THREAD_ID in (413, 414);
      		 
      Empty set (0.001 sec)
      		 
       
      		 
      SELECT *   FROM performance_schema.threads  WHERE processlist_ID in (413, 414);
      		 
      +-----------+---------------------------+------------+----------------+------------------+------------------+----------------+---------------------+------------------+---------------------------------+------------------------------------+------------------+------+--------------+
      		 
      | THREAD_ID | NAME                      | TYPE       | PROCESSLIST_ID | PROCESSLIST_USER | PROCESSLIST_HOST | PROCESSLIST_DB | PROCESSLIST_COMMAND | PROCESSLIST_TIME | PROCESSLIST_STATE               | PROCESSLIST_INFO                   | PARENT_THREAD_ID | ROLE | INSTRUMENTED |
      		 
      +-----------+---------------------------+------------+----------------+------------------+------------------+----------------+---------------------+------------------+---------------------------------+------------------------------------+------------------+------+--------------+
      		 
      |       429 | thread/sql/one_connection | FOREGROUND |            413 | root             | localhost        | test           | Query               |               41 | Waiting for table metadata lock | alter table test add column c9 int |                1 | NULL | YES          |
      		 
      |       430 | thread/sql/one_connection | FOREGROUND |            414 | root             | localhost        | test           | Sleep               |               51 | NULL                            | NULL                               |                1 | NULL | YES          |
      		 
      +-----------+---------------------------+------------+----------------+------------------+------------------+----------------+---------------------+------------------+---------------------------------+------------------------------------+------------------+------+--------------+
      		 
      2 rows in set (0.001 sec)

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            sanja Oleksandr Byelkin
            oli Oli Sennhauser
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              Created:
              Updated:

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