[#MDEV-23882] Document possible LOCK_TYPE values for metadata locks

MariaDB 10.5 introduced yet another way to monitor metadata lock, via performance_schema.metadata_locks table. MySQL manual (https://dev.mysql.com/doc/refman/5.7/en/performance-schema-metadata-locks-table.html) can be used to find out what is presented there, but unfortunately there are different/new metadata lock types introduced in MariaDB and one may get the output like this:

MariaDB [performance_schema]> select * from metadata_locks limit 5\G

*************************** 1. row ***************************

          OBJECT_TYPE: TABLE

        OBJECT_SCHEMA: sbtest

          OBJECT_NAME: sbtest1

OBJECT_INSTANCE_BEGIN: 140032787904800

            LOCK_TYPE: SHARED_WRITE

        LOCK_DURATION: TRANSACTION

          LOCK_STATUS: GRANTED

               SOURCE:

      OWNER_THREAD_ID: 34

       OWNER_EVENT_ID: 1

*************************** 2. row ***************************

          OBJECT_TYPE: BACKUP

        OBJECT_SCHEMA: NULL

          OBJECT_NAME: NULL

OBJECT_INSTANCE_BEGIN: 140032778203712

            LOCK_TYPE: BACKUP_TRANS_DML

        LOCK_DURATION: STATEMENT

          LOCK_STATUS: GRANTED

               SOURCE:

      OWNER_THREAD_ID: 34

       OWNER_EVENT_ID: 1

*************************** 3. row ***************************

          OBJECT_TYPE: TABLE

        OBJECT_SCHEMA: sbtest

          OBJECT_NAME: sbtest1

OBJECT_INSTANCE_BEGIN: 140033249782768

            LOCK_TYPE: SHARED_WRITE

        LOCK_DURATION: TRANSACTION

          LOCK_STATUS: GRANTED

               SOURCE:

      OWNER_THREAD_ID: 33

       OWNER_EVENT_ID: 1

*************************** 4. row ***************************

          OBJECT_TYPE: BACKUP

        OBJECT_SCHEMA: NULL

          OBJECT_NAME: NULL

OBJECT_INSTANCE_BEGIN: 140033248057584

            LOCK_TYPE: BACKUP_TRANS_DML

        LOCK_DURATION: STATEMENT

          LOCK_STATUS: GRANTED

               SOURCE:

      OWNER_THREAD_ID: 33

       OWNER_EVENT_ID: 1

*************************** 5. row ***************************

          OBJECT_TYPE: TABLE

        OBJECT_SCHEMA: sbtest

          OBJECT_NAME: sbtest1

OBJECT_INSTANCE_BEGIN: 140033449398688

            LOCK_TYPE: SHARED_WRITE

        LOCK_DURATION: TRANSACTION

          LOCK_STATUS: GRANTED

               SOURCE:

      OWNER_THREAD_ID: 32

       OWNER_EVENT_ID: 1

5 rows in set (0,001 sec)

that includes BACKUP_TRANS_DML, BACKUP_START, BACKUP_FTWRL1 etc types of locks with OBJECT_TYPE =- BACKUP that upstream documentation does not cover in any way.

This is a request to properly document the content of this new P_S table, including all object rypes and all types of metadata locks with compatibility matrix for them if possible.

[MDEV-23882] Document possible LOCK_TYPE values for metadata locks Created: 2020-10-03 Updated: 2022-03-12
Status:	Open
Project:	MariaDB Server
Component/s:	Backup, Documentation, Performance Schema
Fix Version/s:	10.5

[MDEV-23882] Document possible LOCK_TYPE values for metadata locks Created: 2020-10-03 Updated: 2022-03-12