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


  • 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_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.


SELECT * FROM system.replication_queue LIMIT 1 FORMAT Vertical;
Row 1:
database: merge
table: visits_v2
replica_name: mtgiga001-1t
position: 15
node_name: queue-0009325559
create_time: 2020-12-07 14:04:21
required_quorum: 0
source_replica: mtgiga001-1t
new_part_name: 20201130_121373_121384_2
parts_to_merge: ['20201130_121373_121378_1','20201130_121379_121379_0','20201130_121380_121380_0','20201130_121381_121381_0','20201130_121382_121382_0','20201130_121383_121383_0','20201130_121384_121384_0']
is_detach: 0
is_currently_executing: 0
num_tries: 36
last_exception: Code: 226, e.displayText() = DB::Exception: Marks file '/opt/clickhouse/data/merge/visits_v2/tmp_fetch_20201130_121373_121384_2/CounterID.mrk' does not exist (version (official build))
last_attempt_time: 2020-12-08 17:35:54
num_postponed: 0
last_postpone_time: 1970-01-01 03:00:00

See Also