Contains information about tasks from replication queues stored in 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 ZooKeeper. Different replicas of the same table have different names.

  • position (UInt32) — Position of the task in the queue.

  • node_name (String) — Node name in ZooKeeper.

  • 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 detached folder).
      You may think of it as a GET_PART with some optimisations 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 certain range of partitions and replace them by 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 postponed tasks.

  • 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
position:               15
node_name:              queue-0009325559
type:                   MERGE_PARTS
create_time:            2020-12-07 14:04:21
required_quorum:        0
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' doesn't 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

Original article

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