The Information Schema INNODB_LOCKS table stores information about locks that InnoDB transactions have requested but not yet acquired, or that is blocking another transaction.
It has the following columns:
| Column | Description |
|---|---|
LOCK_ID |
Lock ID number - the format is not fixed, so do not rely upon the number for information. |
LOCK_TRX_ID |
Lock's transaction ID. Matches the INNODB_TRX.TRX_ID column. |
LOCK_MODE |
Lock mode. One of S (shared), X (exclusive), IS (intention shared), IX (intention exclusive row lock), S_GAP (shared gap lock), X_GAP (exclusive gap lock), IS_GAP (intention shared gap lock), IX_GAP (intention exclusive gap lock) or AUTO_INC (auto-increment table level lock). |
LOCK_TYPE |
Whether the lock is RECORD (row level) or TABLE level. |
LOCK_TABLE |
Name of the locked table,or table containing locked rows. |
LOCK_INDEX |
Index name if a RECORD LOCK_TYPE, or NULL if not. |
LOCK_SPACE |
Tablespace ID if a RECORD LOCK_TYPE, or NULL if not. |
LOCK_PAGE |
Locked record page number if a RECORD LOCK_TYPE, or NULL if not. |
LOCK_REC |
Locked record heap number if a RECORD LOCK_TYPE, or NULL if not. |
LOCK_DATA |
Locked record primary key as an SQL string if a RECORD LOCK_TYPE, or NULL if not. If no primary key exists, the internal InnoDB row_id number is instead used. To avoid unnecessary IO, also NULL if the locked record page is not in the buffer pool
|
The table is often used in conjunction with the INNODB_LOCK_WAITS and INNODB_TRX tables to diagnose problematic locks and transactions.
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https://mariadb.com/kb/en/information-schema-innodb_locks-table/