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29.12.16.2 The 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 are not 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:

    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;
  • EFFECTIVE_MAX_TRANSACTIONS_LIMIT

    The effective max_transactions_limit_per_tg value for the group.

  • NUM_QUERY_THREADS

    The number of worker threads in the group.

  • TIME_OF_LAST_THREAD_CREATION

    The point in time when the thread was last created.

  • NUM_CONNECT_HANDLER_THREAD_IN_SLEEP

    The number of inactive connection handler threads.

  • THREADS_BOUND_TO_TRANSACTION

    The number of threads in an active transaction, which must be less than thread_pool_max_transactions_limit; this is set only when thread_pool_max_transactions_limit is not 0.

  • QUERY_THREADS_COUNT

    same as num_query_threads, but used for different purposes?

  • TIME_OF_EARLIEST_CON_EXPIRE

    A timestamp showing the earliest point in time when a connection is expected to expire.

The tp_thread_group_state table has one index; this is a unique index on the TP_GROUP_ID column.

The EFFECTIVE_MAX_TRANSACTIONS_LIMIT, NUM_QUERY_THREADS, TIME_OF_LAST_THREAD_CREATION, NUM_CONNECT_HANDLER_THREAD_IN_SLEEP, THREADS_BOUND_TO_TRANSACTION, QUERY_THREADS_COUNT, and TIME_OF_EARLIEST_CON_EXPIRE columns were added in MySQL 8.3.

TRUNCATE TABLE is not permitted for the tp_thread_group_state table.