Information Schema THREAD_POOL_QUEUES Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_QUEUES table was introduced in MariaDB 10.5.0.

The table provides information about thread pool queues, and contains the following columns:

GROUP_IDthe thread group this row is showing data for
POSITIONposition in the groups queue
PRIORITYrequest priority, see priority scheduling
CONNECTION_IDID of the client connection that submitted the queued request
QUEUEING_TIME_MICROSECONDShow long the request has already been waiting in the queue in microseconds

Setting thread_poll_exact_stats will provides better queueing time statistics by using a high precision timestamp, at a small performance cost, for the time when the connection was added to the queue. This timestamp helps calculate the queuing time shown in the table.

Setting thread_pool_dedicated_listener will give each group its own dedicated listener, and the listener thread will not pick up work items. As a result, the queueing time in the table will be more exact, since IO requests are immediately dequeued from poll, without delay.


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