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94 lines
4.8 KiB
Markdown
94 lines
4.8 KiB
Markdown
---
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slug: /en/operations/system-tables/replication_queue
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---
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# replication_queue
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Contains information about tasks from replication queues stored in ClickHouse Keeper, or ZooKeeper, for tables in the `ReplicatedMergeTree` family.
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Columns:
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- `database` ([String](../../sql-reference/data-types/string.md)) — Name of the database.
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- `table` ([String](../../sql-reference/data-types/string.md)) — Name of the table.
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- `replica_name` ([String](../../sql-reference/data-types/string.md)) — Replica name in ClickHouse Keeper. Different replicas of the same table have different names.
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- `position` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Position of the task in the queue.
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- `node_name` ([String](../../sql-reference/data-types/string.md)) — Node name in ClickHouse Keeper.
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- `type` ([String](../../sql-reference/data-types/string.md)) — Type of the task in the queue, one of:
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- `GET_PART` — Get the part from another replica.
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- `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.
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- `MERGE_PARTS` — Merge the parts.
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- `DROP_RANGE` — Delete the parts in the specified partition in the specified number range.
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- `CLEAR_COLUMN` — NOTE: Deprecated. Drop specific column from specified partition.
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- `CLEAR_INDEX` — NOTE: Deprecated. Drop specific index from specified partition.
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- `REPLACE_RANGE` — Drop a certain range of parts and replace them with new ones.
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- `MUTATE_PART` — Apply one or several mutations to the part.
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- `ALTER_METADATA` — Apply alter modification according to global /metadata and /columns paths.
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- `create_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Date and time when the task was submitted for execution.
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- `required_quorum` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of replicas waiting for the task to complete with confirmation of completion. This column is only relevant for the `GET_PARTS` task.
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- `source_replica` ([String](../../sql-reference/data-types/string.md)) — Name of the source replica.
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- `new_part_name` ([String](../../sql-reference/data-types/string.md)) — Name of the new part.
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- `parts_to_merge` ([Array](../../sql-reference/data-types/array.md) ([String](../../sql-reference/data-types/string.md))) — Names of parts to merge or update.
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- `is_detach` ([UInt8](../../sql-reference/data-types/int-uint.md)) — The flag indicates whether the `DETACH_PARTS` task is in the queue.
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- `is_currently_executing` ([UInt8](../../sql-reference/data-types/int-uint.md)) — The flag indicates whether a specific task is being performed right now.
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- `num_tries` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of failed attempts to complete the task.
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- `last_exception` ([String](../../sql-reference/data-types/string.md)) — Text message about the last error that occurred (if any).
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- `last_attempt_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Date and time when the task was last attempted.
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- `num_postponed` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of postponed tasks.
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- `postpone_reason` ([String](../../sql-reference/data-types/string.md)) — The reason why the task was postponed.
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- `last_postpone_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Date and time when the task was last postponed.
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- `merge_type` ([String](../../sql-reference/data-types/string.md)) — Type of the current merge. Empty if it's a mutation.
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**Example**
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``` sql
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SELECT * FROM system.replication_queue LIMIT 1 FORMAT Vertical;
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```
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``` text
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Row 1:
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──────
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database: merge
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table: visits_v2
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replica_name: mtgiga001-1t
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position: 15
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node_name: queue-0009325559
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type: MERGE_PARTS
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create_time: 2020-12-07 14:04:21
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required_quorum: 0
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source_replica: mtgiga001-1t
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new_part_name: 20201130_121373_121384_2
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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']
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is_detach: 0
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is_currently_executing: 0
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num_tries: 36
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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 20.8.7.15 (official build))
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last_attempt_time: 2020-12-08 17:35:54
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num_postponed: 0
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postpone_reason:
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last_postpone_time: 1970-01-01 03:00:00
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```
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**See Also**
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- [Managing ReplicatedMergeTree Tables](../../sql-reference/statements/system.md#query-language-system-replicated)
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