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system.background_schedule_pool

Querying in ClickHouse Cloud

The data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the clusterAllReplicas function. See here for further details.

Contains information about tasks in background schedule pools. Background schedule pools are used for executing periodic tasks such as distributed sends, buffer flushes, and message broker operations.

Columns:

  • pool (String) — Pool name. Possible values:
    • schedule — General purpose schedule pool
    • buffer_flush — Pool for flushing Buffer table data
    • distributed — Pool for distributed table operations
    • message_broker — Pool for message broker operations
  • database (String) — Database name.
  • table (String) — Table name.
  • table_uuid (UUID) — Table UUID.
  • query_id (String) — Query ID (if executing now) (Note, it is not a real query, but just a randomly generated ID for matching logs in system.text_log).
  • elapsed_ms (UInt64) — Task execution time (if executing now).
  • log_name (String) — Log name for the task.
  • deactivated (UInt8) — Whether the task is deactivated (always false, since deactivated tasks are removed from the pool).
  • scheduled (UInt8) — Whether the task is scheduled for execution.
  • delayed (UInt8) — Whether the task is scheduled with delay.
  • executing (UInt8) — Whether the task is currently executing.

Example

SELECT * FROM system.background_schedule_pool LIMIT 5 FORMAT Vertical;

Row 1:
──────
pool:        distributed
database:    default
table:       data
table_uuid:  00000000-0000-0000-0000-000000000000
query_id:
elapsed_ms:  0
log_name:    BackgroundJobsAssignee:DataProcessing
deactivated: 0
scheduled:   1
delayed:     0
executing:   0

See Also