The Ultimate Guide to High Availability with MariaDB

METADATA_LOCK_INFO Plugin

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MariaDB starting with 10.0.7

The metadata_lock_info plugin was added in MariaDB 10.0.7.

About

This plugin implements a new table, INFORMATION_SCHEMA.METADATA_LOCK_INFO. This table shows active metadata locks.

Installation

To install this plugin, use the INSTALL SONAME or INSTALL PLUGIN commands. For example:

INSTALL SONAME 'metadata_lock_info';

Examples

The table will be empty if there are no active metadata locks.

SELECT * FROM information_schema.metadata_lock_info;
Empty set (0.00 sec)

SELECT * FROM information_schema.metadata_lock_info;  
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+
| THREAD_ID | LOCK_MODE                | LOCK_DURATION | LOCK_TYPE            | TABLE_SCHEMA    | TABLE_NAME  |  
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+
|        31 | MDL_INTENTION_EXCLUSIVE  | MDL_EXPLICIT  | Global read lock     |                 |             |  
|        31 | MDL_INTENTION_EXCLUSIVE  | MDL_EXPLICIT  | Commit lock          |                 |             |
|        31 | MDL_INTENTION_EXCLUSIVE  | MDL_EXPLICIT  | Schema metadata lock | dbname          |             |
|        31 | MDL_SHARED_NO_READ_WRITE | MDL_EXPLICIT  | Table metadata lock  | dbname          | exotics     |
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+
4 rows in set (0.00 sec)

See INFORMATION_SCHEMA.METADATA_LOCK_INFO for information on the table structure.

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