Chapter 21 INFORMATION_SCHEMA Tables

Use these tables to measure the effectiveness of InnoDB table compression in your database.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of these tables including data types and default values.

You must have the PROCESS privilege to query this table.

For usage information, see Section 14.6.4, “Monitoring Compression at Runtime” and Section 14.12.1.3, “Using the Compression Information Schema Tables”. For general information about InnoDB table compression, see Section 14.6, “InnoDB Table Compression”.

Use these tables to measure the effectiveness of InnoDB table compression for specific tables, indexes, or both.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of these tables including data types and default values.

You must have the PROCESS privilege to query these tables.

Because collecting separate measurements for every index imposes substantial performance overhead, INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET statistics are not gathered by default. You must enable the innodb_cmp_per_index_enabled configuration option before performing the operations on compressed tables that you want to monitor.

For usage information, see Section 14.6.4, “Monitoring Compression at Runtime” and Section 14.12.1.3, “Using the Compression Information Schema Tables”. For general information about InnoDB table compression, see Section 14.6, “InnoDB Table Compression”.

Use these tables to measure the effectiveness of InnoDB table compression in your database.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of these tables including data types and default values.

You must have the PROCESS privilege to query this table.

For usage information, see Section 14.6.4, “Monitoring Compression at Runtime” and Section 14.12.1.3, “Using the Compression Information Schema Tables”. For general information about InnoDB table compression, see Section 14.6, “InnoDB Table Compression”.

Use this table to help diagnose performance problems that occur during times of heavy concurrent load. Its contents are updated as described in Section 14.12.2.3, “Data Persistence and Consistency for InnoDB Transaction and Locking Tables”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For usage information, see Section 14.12.2.1, “Usage Examples for InnoDB Transaction and Locking Tables”.

Use this table to help diagnose performance problems that occur during times of heavy concurrent load. Its contents are updated as described in Section 14.12.2.3, “Data Persistence and Consistency for InnoDB Transaction and Locking Tables”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For usage information, see Section 14.12.2.1, “Usage Examples for InnoDB Transaction and Locking Tables”.

Use this table to help diagnose performance problems that occur during times of heavy concurrent load. Its contents are updated as described in Section 14.12.2.3, “Data Persistence and Consistency for InnoDB Transaction and Locking Tables”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For usage information, see Section 14.12.2.1, “Usage Examples for InnoDB Transaction and Locking Tables”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

This table is primarily useful for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

Because tablespace flags are always zero for all Antelope file formats (unlike table flags), there is no way to determine from this flag integer if the tablespace row format is Redundant or Compact. As a result, the possible values for the ROW_FORMAT field are “Compact or Redundant”, “Compressed”, or “Dynamic.”

This table is primarily useful for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

When tables, table rows, partitions, or indexes are deleted, associated pages remain in the buffer pool until space is required for other data. The INNODB_BUFFER_PAGE table reports information about these pages until they are evicted from the buffer pool. For more information about how the InnoDB manages buffer pool data, see Section 8.10.1, “The InnoDB Buffer Pool”.

This table is primarily useful for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

Querying this table can require MySQL to allocate a large block of contiguous memory, more than 64 bytes time the number of active pages in the buffer pool. This allocation could potentially cause an out-of-memory error, especially for systems with multi-gigabyte buffer pools.

Querying this table requires MySQL to lock the data structure representing the buffer pool while traversing the LRU list, which can reduce concurrency, especially for systems with multi-gigabyte buffer pools.

When tables, table rows, partitions, or indexes are deleted, associated pages remain in the buffer pool until space is required for other data. The INNODB_BUFFER_PAGE_LRU table reports information about these pages until they are evicted from the buffer pool. For more information about how the InnoDB manages buffer pool data, see Section 8.10.1, “The InnoDB Buffer Pool”.

This table is primarily useful for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

You must have the PROCESS privilege to query this table.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

This table is only intended for internal configuration. It is not intended for statistical information purposes.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

The values for the KEY column might evolve depending on the needs for performance tuning and debugging for InnoDB full-text processing. Currently, the key values include:

For more information about InnoDB FULLTEXT search, see Section 14.2.6.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For more information about InnoDB FULLTEXT search, see Section 14.2.6.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

This table initially appears empty, until you set the value of the configuration variable innodb_ft_aux_table. The following example demonstrates how to use the innodb_ft_aux_table option to show information about a FULLTEXT index for a specified table. Before information for newly inserted rows appears in INNODB_FT_INDEX_TABLE, the FULLTEXT index cache must be flushed to disk. This is accomplished by running an OPTIMIZE TABLE operation on the indexed table with innodb_optimize_fulltext_only=ON.

mysql> use test;

mysql> CREATE TABLE articles (
      id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
      title VARCHAR(200),
      body TEXT,
      FULLTEXT (title,body)
    ) ENGINE=InnoDB;

mysql> INSERT INTO articles (title,body) VALUES
    ('MySQL Tutorial','DBMS stands for DataBase ...'),
    ('How To Use MySQL Well','After you went through a ...'),
    ('Optimizing MySQL','In this tutorial we will show ...'),
    ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'),
    ('MySQL vs. YourSQL','In the following database comparison ...'),
    ('MySQL Security','When configured properly, MySQL ...');

mysql> SET GLOBAL innodb_optimize_fulltext_only=ON;
Query OK, 0 rows affected (0.00 sec)

mysql> OPTIMIZE TABLE articles;
+---------------+----------+----------+----------+
| Table         | Op       | Msg_type | Msg_text |
+---------------+----------+----------+----------+
| test.articles | optimize | status   | OK       |
+---------------+----------+----------+----------+
1 row in set (0.00 sec)

mysql> SET GLOBAL innodb_ft_aux_table = 'test/articles';
Query OK, 0 rows affected (0.00 sec)

mysql> USE INFORMATION_SCHEMA;

mysql> SELECT word, doc_count, doc_id, position FROM INNODB_FT_INDEX_TABLE LIMIT 5;
+------------+-----------+--------+----------+
| word       | doc_count | doc_id | position |
+------------+-----------+--------+----------+
| 1001       |         1 |      4 |        0 |
| after      |         1 |      2 |       22 |
| comparison |         1 |      5 |       44 |
| configured |         1 |      6 |       20 |
| database   |         2 |      1 |       31 |
+------------+-----------+--------+----------+
5 rows in set (0.01 sec)
        

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For more information about InnoDB FULLTEXT search, see Section 14.2.6.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

This table initially appears empty, until you set the value of the configuration variable innodb_ft_aux_table. The following example demonstrates how to use the innodb_ft_aux_table option to show information about a FULLTEXT index for a specified table.

mysql> USE test;

mysql> CREATE TABLE articles (
      id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
      title VARCHAR(200),
      body TEXT,
      FULLTEXT (title,body)
    ) ENGINE=InnoDB;

mysql> INSERT INTO articles (title,body) VALUES
    ('MySQL Tutorial','DBMS stands for DataBase ...'),
    ('How To Use MySQL Well','After you went through a ...'),
    ('Optimizing MySQL','In this tutorial we will show ...'),
    ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'),
    ('MySQL vs. YourSQL','In the following database comparison ...'),
    ('MySQL Security','When configured properly, MySQL ...');

mysql> SET GLOBAL innodb_ft_aux_table = 'test/articles';
Query OK, 0 rows affected (0.00 sec)

mysql> USE INFORMATION_SCHEMA;

mysql> SELECT word, doc_count, doc_id, position FROM INNODB_FT_INDEX_CACHE LIMIT 5;
+------------+-----------+--------+----------+
| word       | doc_count | doc_id | position |
+------------+-----------+--------+----------+
| 1001       |         1 |      4 |        0 |
| after      |         1 |      2 |       22 |
| comparison |         1 |      5 |       44 |
| configured |         1 |      6 |       20 |
| database   |         2 |      1 |       31 |
+------------+-----------+--------+----------+
5 rows in set (0.00 sec)
        

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For more information about InnoDB FULLTEXT search, see Section 14.2.6.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For more information about InnoDB FULLTEXT search, see Section 14.2.6.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

Use DESCRIBE or SHOW COLUMNS to view additional information about the columns of this table including data types and default values.

You must have the PROCESS privilege to query this table.

For more information about InnoDB FULLTEXT search, see Section 14.2.6.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

FILE_ID column values are auto-generated.

FILE_NAME is the name of an UNDO log file created by CREATE LOGFILE GROUP or ALTER LOGFILE GROUP, or of a data file created by CREATE TABLESPACE or ALTER TABLESPACE.

FILE_TYPE is one of the values UNDOFILE, DATAFILE, or TABLESPACE.

TABLESPACE_NAME is the name of the tablespace with which the file is associated.

Currently, the value of the TABLESPACE_CATALOG column is always NULL.

TABLE_NAME is the name of the Disk Data table with which the file is associated, if any.

The LOGFILE_GROUP_NAME column gives the name of the log file group to which the log file or data file belongs.

For an UNDO log file, the LOGFILE_GROUP_NUMBER contains the auto-generated ID number of the log file group to which the log file belongs.

For a MySQL Cluster Disk Data log file or data file, the value of the ENGINE column is always NDB or NDBCLUSTER.

For a MySQL Cluster Disk Data log file or data file, the value of the FULLTEXT_KEYS column is always empty.

The FREE EXTENTS column displays the number of extents which have not yet been used by the file. The TOTAL EXTENTS column show the total number of extents allocated to the file.

The difference between these two columns is the number of extents currently in use by the file:

SELECT TOTAL_EXTENTS - FREE_EXTENTS AS extents_used
    FROM INFORMATION_SCHEMA.FILES
    WHERE FILE_NAME = 'myfile.dat';

You can approximate the amount of disk space in use by the file by multiplying this difference by the value of the EXTENT_SIZE column, which gives the size of an extent for the file in bytes:

SELECT (TOTAL_EXTENTS - FREE_EXTENTS) * EXTENT_SIZE AS bytes_used
    FROM INFORMATION_SCHEMA.FILES
    WHERE FILE_NAME = 'myfile.dat';

Similarly, you can estimate the amount of space that remains available in a given file by multiplying FREE_EXTENTS by EXTENT_SIZE:

SELECT FREE_EXTENTS * EXTENT_SIZE AS bytes_free
    FROM INFORMATION_SCHEMA.FILES
    WHERE FILE_NAME = 'myfile.dat';

It is also important to remember that once an extent is used, it cannot be freed again without dropping the data file of which it is a part. This means that deletes from a Disk Data table do not release disk space.

The extent size can be set in a CREATE TABLESPACE statement. See Section 13.1.18, “CREATE TABLESPACE Syntax”, for more information.

The INITIAL_SIZE column shows the size in bytes of the file. This is the same value that was used in the INITIAL_SIZE clause of the CREATE LOGFILE GROUP, ALTER LOGFILE GROUP, CREATE TABLESPACE, or ALTER TABLESPACE statement used to create the file.

For MySQL Cluster Disk Data files, the value of the MAXIMUM_SIZE column is always the same as INITIAL_SIZE, and the AUTOEXTEND_SIZE column is always empty.

The CREATION_TIME column shows the date and time when the file was created. The LAST_UPDATE_TIME column displays the date and time when the file was last modified. The LAST_ACCESSED column provides the date and time when the file was last accessed by the server.

Currently, the values of these columns are as reported by the operating system, and are not supplied by the NDB storage engine. Where no value is provided by the operating system, these columns display 0000-00-00 00:00:00.

For MySQL Cluster Disk Data files, the value of the RECOVER_TIME and TRANSACTION_COUNTER columns is always 0.

For MySQL Cluster Disk Data files, the following columns are always NULL:

For MySQL Cluster Disk Data files, the value of the STATUS column is always NORMAL.

For MySQL Cluster Disk Data files, the EXTRA column shows which data node the file belongs to, as each data node has its own copy of the file. Suppose that you use this statement on a MySQL Cluster with four data nodes:

CREATE LOGFILE GROUP mygroup
    ADD UNDOFILE 'new_undo.dat'
    INITIAL_SIZE 2G
    ENGINE NDB;

After running the CREATE LOGFILE GROUP statement successfully, you should see a result similar to the one shown here for this query against the FILES table:

mysql> SELECT LOGFILE_GROUP_NAME, FILE_TYPE, EXTRA
    ->     FROM INFORMATION_SCHEMA.FILES
    ->     WHERE FILE_NAME = 'new_undo.dat';
+--------------------+-------------+----------------+
| LOGFILE_GROUP_NAME | FILE_TYPE   | EXTRA          |
+--------------------+-------------+----------------+
| mygroup            | UNDO FILE   | CLUSTER_NODE=3 |
| mygroup            | UNDO FILE   | CLUSTER_NODE=4 |
| mygroup            | UNDO FILE   | CLUSTER_NODE=5 |
| mygroup            | UNDO FILE   | CLUSTER_NODE=6 |
+--------------------+-------------+----------------+
4 rows in set (0.01 sec)

The FILES table is a nonstandard table.

An additional row is present in the FILES table following the creation of a logfile group. This row has NULL for the value of the FILE_NAME column. For this row, the value of the FILE_ID column is always 0, that of the FILE_TYPE column is always UNDO FILE, and that of the STATUS column is always NORMAL. Currently, the value of the ENGINE column is always NDBCLUSTER.

The FREE_EXTENTS column in this row shows the total number of free extents available to all undo files belonging to a given log file group whose name and number are shown in the LOGFILE_GROUP_NAME and LOGFILE_GROUP_NUMBER columns, respectively.

Suppose there are no existing log file groups on your MySQL Cluster, and you create one using the following statement:

mysql> CREATE LOGFILE GROUP lg1
    ->   ADD UNDOFILE 'undofile.dat'
    ->   INITIAL_SIZE = 16M
    ->   UNDO_BUFFER_SIZE = 1M
    ->   ENGINE = NDB;
Query OK, 0 rows affected (3.81 sec)

You can now see this NULL row when you query the FILES table:

mysql> SELECT DISTINCT
    ->   FILE_NAME AS File,
    ->   FREE_EXTENTS AS Free,
    ->   TOTAL_EXTENTS AS Total,
    ->   EXTENT_SIZE AS Size,
    ->   INITIAL_SIZE AS Initial
    ->   FROM INFORMATION_SCHEMA.FILES;
+--------------+---------+---------+------+----------+
| File         | Free    | Total   | Size | Initial  |
+--------------+---------+---------+------+----------+
| undofile.dat |    NULL | 4194304 |    4 | 16777216 |
| NULL         | 4184068 |    NULL |    4 |     NULL |
+--------------+---------+---------+------+----------+
2 rows in set (0.01 sec)

The total number of free extents available for undo logging is always somewhat less than the sum of the TOTAL_EXTENTS column values for all undo files in the log file group due to overhead required for maintaining the undo files. This can be seen by adding a second undo file to the log file group, then repeating the previous query against the FILES table:

mysql> ALTER LOGFILE GROUP lg1
    ->   ADD UNDOFILE 'undofile02.dat'
    ->   INITIAL_SIZE = 4M
    ->   ENGINE = NDB;
Query OK, 0 rows affected (1.02 sec)

mysql> SELECT DISTINCT
    ->   FILE_NAME AS File,
    ->   FREE_EXTENTS AS Free,
    ->   TOTAL_EXTENTS AS Total,
    ->   EXTENT_SIZE AS Size,
    ->   INITIAL_SIZE AS Initial
    ->   FROM INFORMATION_SCHEMA.FILES;
+----------------+---------+---------+------+----------+
| File           | Free    | Total   | Size | Initial  |
+----------------+---------+---------+------+----------+
| undofile.dat   |    NULL | 4194304 |    4 | 16777216 |
| undofile02.dat |    NULL | 1048576 |    4 |  4194304 |
| NULL           | 5223944 |    NULL |    4 |     NULL |
+----------------+---------+---------+------+----------+
3 rows in set (0.01 sec)

The amount of free space in bytes which is available for undo logging by Disk Data tables using this log file group can be approximated by multiplying the number of free extents by the initial size:

mysql> SELECT
    ->   FREE_EXTENTS AS 'Free Extents',
    ->   FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
    ->   FROM INFORMATION_SCHEMA.FILES
    ->   WHERE LOGFILE_GROUP_NAME = 'lg1'
    ->   AND FILE_NAME IS NULL;
+--------------+------------+
| Free Extents | Free Bytes |
+--------------+------------+
|      5223944 |   20895776 |
+--------------+------------+
1 row in set (0.02 sec)

If you create a MySQL Cluster Disk Data table and then insert some rows into it, you can see approximately how much space remains for undo logging afterward, for example:

mysql> CREATE TABLESPACE ts1
    ->   ADD DATAFILE 'data1.dat'
    ->   USE LOGFILE GROUP lg1
    ->   INITIAL_SIZE 512M
    ->   ENGINE = NDB;
Query OK, 0 rows affected (8.71 sec)

mysql> CREATE TABLE dd (
    ->   c1 INT NOT NULL PRIMARY KEY,
    ->   c2 INT,
    ->   c3 DATE
    ->   )
    ->   TABLESPACE ts1 STORAGE DISK
    ->   ENGINE = NDB;
Query OK, 0 rows affected (2.11 sec)

mysql> INSERT INTO dd VALUES
    ->   (NULL, 1234567890, '2007-02-02'),
    ->   (NULL, 1126789005, '2007-02-03'),
    ->   (NULL, 1357924680, '2007-02-04'),
    ->   (NULL, 1642097531, '2007-02-05');
Query OK, 4 rows affected (0.01 sec)

mysql> SELECT
    ->   FREE_EXTENTS AS 'Free Extents',
    ->   FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
    ->   FROM INFORMATION_SCHEMA.FILES
    ->   WHERE LOGFILE_GROUP_NAME = 'lg1'
    ->   AND FILE_NAME IS NULL;
+--------------+------------+
| Free Extents | Free Bytes |
+--------------+------------+
|      5207565 |   20830260 |
+--------------+------------+
1 row in set (0.01 sec)

An additional row is present in the FILES table for any MySQL Cluster tablespace, whether or not any data files are associated with the tablespace. This row has NULL for the value of the FILE_NAME column. For this row, the value of the FILE_ID column is always 0, that of the FILE_TYPE column is always TABLESPACE, and that of the STATUS column is always NORMAL. Currently, the value of the ENGINE column is always NDBCLUSTER.

There are no SHOW statements associated with the FILES table.

For additional information, and examples of creating and dropping MySQL Cluster Disk Data objects, see Section 18.5.12, “MySQL Cluster Disk Data Tables”.

TP_GROUP_ID

The thread group ID.

TP_THREAD_NUMBER

The ID of the thread within its thread group. TP_GROUP_ID and TP_THREAD_NUMBER together provide a unique key within the table.

PROCESS_COUNT

The 10ms interval in which the statement that uses this thread is currently executing. 0 means no statement is executing, 1 means it is in the first 10ms, and so forth.

WAIT_TYPE

The type of wait for the thread. NULL means the thread is not blocked. Otherwise, the thread is blocked by a call to thd_wait_begin() and the value specifies the type of wait. The xxx_WAIT columns of the TP_THREAD_GROUP_STATS table accumulate counts for each wait type.

The WAIT_TYPE value is a string that describes the type of wait, as shown in the following table.

TP_GROUP_ID

The thread group ID. This is a unique key within the table.

CONSUMER THREADS

The number of consumer threads. There is at most one thread ready to start executing if the active threads become stalled or blocked.

RESERVE_THREADS

The number of threads in the reserved state. This means that they will not be started until there is a need to wake a new thread and there is no consumer thread. This is where most threads end up when the thread group has created more threads than needed for normal operation. Often a thread group needs additional threads for a short while and then does not need them again for a while. In this case, they go into the reserved state and remain until needed again. They take up some extra memory resources, but no extra computing resources.

CONNECTION_COUNT

The number of connections using this thread group.

QUEUED_QUERIES

The number of statements waiting in the high-priority queue.

QUEUED_TRANSACTIONS

The number of statements waiting in the low-priority queue. These are the initial statements for transactions that have not started, so they also represent queued transactions.

STALL_LIMIT

The value of the thread_pool_stall_limit variable on the thread group. This is the same value for all thread groups.

PRIO_KICKUP_TIMER

The value of the thread_pool_prio_kickup_timer on the thread group. This is the same value for all thread groups.

ALGORITHM

The value of the thread_pool_algorithm on the thread group. This is the same value for all thread groups.

THREAD_COUNT

The number of threads started in the thread pool as part of this thread group.

ACTIVE_THREAD_COUNT

The number of threads active executing statements.

MAX_THREAD_IDS_IN_GROUP

The maximum thread ID of the threads in the group. This is the same as MAX(TP_THREAD_NUMBER) for the threads when selected from the TP_THREAD_GROUP_STATE table. That is, these two queries are equivalent:

SELECT TP_GROUP_ID, MAX_THREAD_IDS_IN_GROUP
FROM TP_THREAD_GROUP_STATE;

SELECT TP_GROUP_ID, MAX(TP_THREAD_NUMBER)
FROM TP_THREAD_STATE GROUP BY TP_GROUP_ID;

STALLED_THREAD_COUNT

The number of stalled statements in the thread group. A stalled statement could be executing, but from a thread pool perspective it is stalled and making no progress. A long-running statement quickly ends up in this category.

WAITING_THREAD_NUMBER

If there is a thread handling the polling of statements in the thread group, this specifies the thread number within this thread group. It is possible that this thread could be executing a statement.

OLDEST_QUEUED

How long in milliseconds the oldest queued statement has been waiting for execution.

TP_GROUP_ID

The thread group ID. This is a unique key within the table.

CONNECTIONS_STARTED

The number of connections started.

CONNECTIONS_CLOSED

The number of connections closed.

QUERIES_EXECUTED

The number of statements executed. This number is incremented when a statement starts executing, not when it finishes.

QUERIES_QUEUED

The number of statements received that were queued for execution. This does not count statements that the thread group was able to begin executing immediately without queuing, which can happen under the conditions described in Section 8.12.7.2, “Thread Pool Operation”.

THREADS_STARTED

The number of threads started.

PRIO_KICKUPS

The number of statements that have been moved from low-priority queue to high-priority queue based on the value of the thread_pool_prio_kickup_timer system variable. If this number increases quickly, consider increasing the value of that variable. A quickly increasing counter means that the priority system is not keeping transactions from starting too early. For InnoDB, this most likely means deteriorating performance due to too many concurrent transactions..