Extended Statistics
The statistics listed in the table below are present in the following management views found in the information_schema database:
mv_activities_extendedmv_activities_extended_cumulativemv_finished_tasksmv_tasks
Column name | Description |
|---|---|
| Wall clock milliseconds elapsed during execution. This is likely to exceed the observed latency of a set of tasks because the tasks are likely to have executed concurrently. |
| Milliseconds spent running on all the CPUs across the cluster. |
| Milliseconds spent waiting for a CPU to become available. A non-zero value indicates that there were more concurrent tasks in the workload than there were CPUs on which to run them. If this value is a significant fraction of elapsed time, the workload is likely issuing its queries faster than the hardware can handle. Investigate the tasks with the highest |
| Bytes read from the filesystem. |
| Bytes written to the filesystem. |
| Bytes actually read from physical disk. This may be higher or lower than the logical number due to hardware and operating system artifacts and optimizations. Note that this column is also an Advanced Statistics, and requires that the global variable |
| Bytes actually written to physical disk. This may be higher or lower than the logical number due to hardware and operating system artifacts and optimizations. Note that this column is also an Advanced Statistics, and requires that the global variable |
| Milliseconds spent waiting for physical disk I/O to complete. If this value is high, it may indicate excessive time to commit transactions to storage. You may need hardware which supports a faster write rate, or you may need to investigate whether other processes are issuing too much I/O and introducing unwanted variability. Check which other activities are using |
| Milliseconds spent waiting on table row locks. |
| Milliseconds spent waiting on locks and condition variables, excluding row locks. This isn’t solely wait time due to contention on data structures because it also includes some time spent waiting for events in general. |
| Milliseconds spent waiting for transaction log records to be flushed to disk. If this value is nonzero, it is usually indicative of disk issues. See |
| Milliseconds spent waiting for space in the transaction log buffer. If this value is nonzero, it is usually indicative of disk issues. See |
| Bytes written to the transaction log buffer. These will eventually be flushed to disk by log flusher system tasks, whose |
| |
| Number of page faults which required disk I/O to resolve. Note that this column is also an Advanced Statistics, and requires that the global variable |
| Bytes received from a socket. |
| Bytes written to a socket. |
| Milliseconds spent waiting for sockets to be ready to send or receive data. This may indicate that leaves are slow to respond to a query, or that a distributed join involves a large data transfer. If this counter has a noticeable delay, check what other activities are consuming |