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ClickHouse/docs/en/operations/system-tables/replication_queue.md
Mike Kot 831b90f272 Replaced the iteration algorithm in part finder 
Now, instead of iterating through the directories, we iterate though
directories of on of the table disks (which doesn't give us a
substantial boost but is a bit neater to read).

- Updated the system.replication_queue command types.
- Fixed the part ptr being empty (added the checksum loading and
initialization).
- Removed extra logging.
2021-03-17 16:55:26 +03:00

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system.replication_queue

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

Columns:

  • 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.

Example

SELECT * FROM system.replication_queue LIMIT 1 FORMAT Vertical;

Row 1:
──────
database:               merge
table:                  visits_v2
replica_name:           mtgiga001-1t.metrika.yandex.net
position:               15
node_name:              queue-0009325559
type:                   MERGE_PARTS
create_time:            2020-12-07 14:04:21
required_quorum:        0
source_replica:         mtgiga001-1t.metrika.yandex.net
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 20.8.7.15 (official build))
last_attempt_time:      2020-12-08 17:35:54
num_postponed:          0
postpone_reason:
last_postpone_time:     1970-01-01 03:00:00

See Also

Original article