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26.12.15.1 The tp_thread_group_state Table

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Note

The Performance Schema table described here is available as of MySQL 8.0.14. Prior to MySQL 8.0.14, use the corresponding INFORMATION_SCHEMA table instead; see Section 25.40.1, “The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table”.

The tp_thread_group_state table has one row per thread group in the thread pool. Each row provides information about the current state of a group.

The tp_thread_group_state table has these columns:

  • 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.

  • CONNECT_THREAD_COUNT

    The number of threads that are processing or waiting to process connection initialization and authentication. There can be a maximum of four connection threads per thread group; these threads expire after a period of inactivity.

  • 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 system variable for the thread group. This is the same value for all thread groups.

  • PRIO_KICKUP_TIMER

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

  • ALGORITHM

    The value of the thread_pool_algorithm system variable for 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 in executing statements.

  • 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.

  • 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_state table. That is, these two queries are equivalent:

    1. SELECT TP_GROUP_ID, MAX_THREAD_IDS_IN_GROUP
    2. FROM tp_thread_group_state;
    3.  
    4. SELECT TP_GROUP_ID, MAX(TP_THREAD_NUMBER)
    5. FROM tp_thread_state GROUP BY TP_GROUP_ID;

The tp_thread_group_state table has these indexes:

  • Unique index on (TP_GROUP_ID)

TRUNCATE TABLE is not permitted for the tp_thread_group_state table.


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Document créé le 26/06/2006, dernière modification le 26/10/2018
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