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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.

Description​

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: this is not a real query, but 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​