Information Schema INNODB_LOCKS Table
The Information Schema INNODB_LOCKS table stores information about locks that InnoDB transactions have requested but not yet acquired, or that are 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
Example
-- session 1
START TRANSACTION;
UPDATE t SET id = 15 WHERE id = 10;
-- session 2
DELETE FROM t WHERE id = 10;
-- session 1
USE information_schema;
SELECT l.*, t.*
FROM information_schema.INNODB_LOCKS l
JOIN information_schema.INNODB_TRX t
ON l.lock_trx_id = t.trx_id
WHERE trx_state = 'LOCK WAIT' \G
*************************** 1. row ***************************
lock_id: 840:40:3:2
lock_trx_id: 840
lock_mode: X
lock_type: RECORD
lock_table: `test`.`t`
lock_index: PRIMARY
lock_space: 40
lock_page: 3
lock_rec: 2
lock_data: 10
trx_id: 840
trx_state: LOCK WAIT
trx_started: 2019-12-23 18:43:46
trx_requested_lock_id: 840:40:3:2
trx_wait_started: 2019-12-23 18:43:46
trx_weight: 2
trx_mysql_thread_id: 46
trx_query: DELETE FROM t WHERE id = 10
trx_operation_state: starting index read
trx_tables_in_use: 1
trx_tables_locked: 1
trx_lock_structs: 2
trx_lock_memory_bytes: 1136
trx_rows_locked: 1
trx_rows_modified: 0
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
trx_unique_checks: 1
trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
trx_is_read_only: 0
trx_autocommit_non_locking: 0
.
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