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Description

Contains information about tasks from replication queues stored in ClickHouse Keeper, or ZooKeeper, for tables in the ReplicatedMergeTree family.

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Columns

  • database (String) — Name of the database.
  • table (String) — Name of the table.
  • replica_name (String) — Replica name in ClickHouse Keeper. Different replicas of the same table have different names.
  • position (UInt32) — Position of the task in the queue.
  • node_name (String) — Node name in ClickHouse Keeper.
  • type (String) — Type of the task in the queue, one of: • GET_PART — Get the part from another replica, • ATTACH_PART — Attach the part, possibly from our own replica (if found in the detached folder). You may think of it as a GET_PART with some optimizations as they’re nearly identical, • MERGE_PARTS — Merge the parts, • DROP_RANGE — Delete the parts in the specified partition in the specified number range. • CLEAR_COLUMN — NOTE: Deprecated. Drop specific column from specified partition. • CLEAR_INDEX — NOTE: Deprecated. Drop specific index from specified partition. • REPLACE_RANGE — Drop a certain range of parts and replace them with new ones. • MUTATE_PART — Apply one or several mutations to the part. • ALTER_METADATA — Apply alter modification according to global /metadata and /columns paths.
  • create_time (DateTime) — Date and time when the task was submitted for execution.
  • required_quorum (UInt32) — The number of replicas waiting for the task to complete with confirmation of completion. This column is only relevant for the GET_PARTS task.
  • source_replica (String) — Name of the source replica.
  • new_part_name (String) — Name of the new part.
  • parts_to_merge (Array(String)) — Names of parts to merge or update.
  • is_detach (UInt8) — The flag indicates whether the DETACH_PARTS task is in the queue.
  • is_currently_executing (UInt8) — The flag indicates whether a specific task is being performed right now.
  • num_tries (UInt32) — The number of failed attempts to complete the task.
  • last_exception (String) — Text message about the last error that occurred (if any).
  • last_exception_time (DateTime) — Date and time when the last error occurred.
  • last_attempt_time (DateTime) — Date and time when the task was last attempted.
  • num_postponed (UInt32) — The number of times the action was postponed.
  • postpone_reason (String) — The reason why the task was postponed.
  • last_postpone_time (DateTime) — Date and time when the task was last postponed.
  • merge_type (String) — Type of the current merge. Empty if it’s a mutation.

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Example

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See Also

Last modified on July 2, 2026