SingleStore DB

Extended Statistics

The statistics listed in the table below are present in the following management views found in the information_schema database:

  • mv_activities_extended

  • mv_activities_extended_cumulative

  • mv_finished_tasks

  • mv_tasks

Column name

Description

elapsed_time_ms

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.

cpu_time_ms

Milliseconds spent running on all the CPUs across the cluster.

cpu_wait_time_ms

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 cpu_time_ms and optimize the relevant queries, reduce your workload, or provision more CPUs for your cluster. Note that this column is also an Advanced Statistics, and requires that the global variable read_advanced_counters is set to ON.

disk_logical_read_b

Bytes read from the filesystem.

disk_logical_write_b

Bytes written to the filesystem.

disk_physical_read_b

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 read_advanced_counters is set to ON.

disk_physical_write_b

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 read_advanced_counters is set to ON.

disk_time_ms

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 disk_physical_read_b or disk_physical_write_b. Note that this column is also an Advanced Statistics, and requires that the global variable read_advanced_counters is set to ON.

lock_row_time_ms

Milliseconds spent waiting on table row locks.

lock_time_ms

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.

log_flush_time_ms

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 disk_time_ms.

log_buffer_time_ms

Milliseconds spent waiting for space in the transaction log buffer. If this value is nonzero, it is usually indicative of disk issues. See disk_time_ms.

log_buffer_b

Bytes written to the transaction log buffer. These will eventually be flushed to disk by log flusher system tasks, whose disk_logical_write_b should include this quantity.

memory_bs

Byte-seconds of memory used.

memory_major_faults

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 read_advanced_counters is set to ON.

network_logical_recv_b

Bytes received from a socket.

network_logical_send_b

Bytes written to a socket.

network_time_ms

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 network_logical_recv_b and network_logical_send_b.