Details
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Bug
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Status: Open (View Workflow)
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Minor
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Resolution: Unresolved
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10.4.8
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n.a.
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;
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+-----------+-------------------------+---------------+----------------------+--------------+------------+
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| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
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+-----------+-------------------------+---------------+----------------------+--------------+------------+
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| 413 | MDL_BACKUP_ALTER_COPY | NULL | Backup lock | | |
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| 414 | MDL_SHARED_READ | NULL | Table metadata lock | test | test |
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| 413 | MDL_SHARED_UPGRADABLE | NULL | Table metadata lock | test | test |
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| 413 | MDL_INTENTION_EXCLUSIVE | NULL | Schema metadata lock | test | |
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+-----------+-------------------------+---------------+----------------------+--------------+------------+
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|
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SELECT *
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-> FROM performance_schema.threads
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-> WHERE THREAD_ID in (413, 414);
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Empty set (0.001 sec)
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SELECT * FROM performance_schema.threads WHERE processlist_ID in (413, 414);
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+-----------+---------------------------+------------+----------------+------------------+------------------+----------------+---------------------+------------------+---------------------------------+------------------------------------+------------------+------+--------------+
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| 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 |
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+-----------+---------------------------+------------+----------------+------------------+------------------+----------------+---------------------+------------------+---------------------------------+------------------------------------+------------------+------+--------------+
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| 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 |
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| 430 | thread/sql/one_connection | FOREGROUND | 414 | root | localhost | test | Sleep | 51 | NULL | NULL | 1 | NULL | YES |
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+-----------+---------------------------+------------+----------------+------------------+------------------+----------------+---------------------+------------------+---------------------------------+------------------------------------+------------------+------+--------------+
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2 rows in set (0.001 sec)
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