21.30.13 The INFORMATION_SCHEMA INNODB

21.30.13 The INFORMATION_SCHEMA INNODB_LOCKS Table

The INNODB_LOCKS table provides information about each lock that an InnoDB transaction has requested but not yet acquired, and each lock that a transaction holds that is blocking another transaction.

The INNODB_LOCKS table has these columns:

LOCK_ID
A unique lock ID number, internal to InnoDB. Treat it as an opaque string. Although LOCK_ID currently contains TRX_ID, the format of the data in LOCK_ID is subject to change at any time. Do not write applications that parse the LOCK_ID value.
LOCK_TRX_ID
The ID of the transaction holding the lock. To obtain details about the transaction, join this column with the TRX_ID column of the INNODB_TRX table.
LOCK_MODE
How the lock is requested. Permitted lock mode descriptors are S, X, IS, IX, GAP, AUTO_INC, and UNKNOWN. Lock mode descriptors may be used in combination to identify particular lock modes. For information about InnoDB lock modes, see Section 14.7.1, “InnoDB Locking”.
LOCK_TYPE
The type of lock. Permitted values are RECORD for a row-level lock, TABLE for a table-level lock.
LOCK_TABLE
The name of the table that has been locked or contains locked records.
LOCK_INDEX
The name of the index, if LOCK_TYPE is RECORD; otherwise NULL.
LOCK_SPACE
The tablespace ID of the locked record, if LOCK_TYPE is RECORD; otherwise NULL.
LOCK_PAGE
The page number of the locked record, if LOCK_TYPE is RECORD; otherwise NULL.
LOCK_REC
The heap number of the locked record within the page, if LOCK_TYPE is RECORD; otherwise NULL.
LOCK_DATA
The data associated with the lock, if any. A value is shown if the LOCK_TYPE is RECORD, otherwise the value is NULL. Primary key values of the locked record are shown for a lock placed on the primary key index. Secondary index values of the locked record are shown for a lock placed on a unique secondary index. Secondary index values are shown with primary key values appended if the secondary index is not unique. If there is no primary key, LOCK_DATA shows either the key values of a selected unique index or the unique InnoDB internal row ID number, according to the rules governing InnoDB clustered index use (see Section 14.6.2.1, “Clustered and Secondary Indexes”). LOCK_DATA reports “supremum pseudo-record” for a lock taken on a supremum pseudo-record. If the page containing the locked record is not in the buffer pool because it was written to disk while the lock was held, InnoDB does not fetch the page from disk. Instead, LOCK_DATA reports NULL.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS\G
*************************** 1. row ***************************
    lock_id: 3723:72:3:2
lock_trx_id: 3723
  lock_mode: X
  lock_type: RECORD
 lock_table: `mysql`.`t`
 lock_index: PRIMARY
 lock_space: 72
  lock_page: 3
   lock_rec: 2
  lock_data: 1, 9
*************************** 2. row ***************************
    lock_id: 3722:72:3:2
lock_trx_id: 3722
  lock_mode: S
  lock_type: RECORD
 lock_table: `mysql`.`t`
 lock_index: PRIMARY
 lock_space: 72
  lock_page: 3
   lock_rec: 2
  lock_data: 1, 9

Notes

Use this table to help diagnose performance problems that occur during times of heavy concurrent load. Its contents are updated as described in Section 14.15.2.3, “Persistence and Consistency of InnoDB Transaction and Locking Information”.
You must have the PROCESS privilege to query this table.
Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.
For usage information, see Section 14.15.2.1, “Using InnoDB Transaction and Locking Information”.