system.metrics

Contains metrics which can be calculated instantly, or have a current value. For example, the number of simultaneously processed queries or the current replica delay. This table is always up to date.

Columns:

  • metric (String) — Metric name.
  • value (Int64) — Metric value.
  • description (String) — Metric description.

The list of supported metrics you can find in the src/Common/CurrentMetrics.cpp source file of ClickHouse.

Example

  1. SELECT * FROM system.metrics LIMIT 10
  1. ┌─metric─────────────────────┬─value─┬─description──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
  2. Query 1 Number of executing queries
  3. Merge 0 Number of executing background merges
  4. PartMutation 0 Number of mutations (ALTER DELETE/UPDATE)
  5. ReplicatedFetch 0 Number of data parts being fetched from replicas
  6. ReplicatedSend 0 Number of data parts being sent to replicas
  7. ReplicatedChecks 0 Number of data parts checking for consistency
  8. BackgroundPoolTask 0 Number of active tasks in BackgroundProcessingPool (merges, mutations, fetches, or replication queue bookkeeping)
  9. BackgroundSchedulePoolTask 0 Number of active tasks in BackgroundSchedulePool. This pool is used for periodic ReplicatedMergeTree tasks, like cleaning old data parts, altering data parts, replica re-initialization, etc.
  10. DiskSpaceReservedForMerge 0 Disk space reserved for currently running background merges. It is slightly more than the total size of currently merging parts.
  11. DistributedSend 0 Number of connections to remote servers sending data that was INSERTed into Distributed tables. Both synchronous and asynchronous mode.
  12. └────────────────────────────┴───────┴──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

See Also