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docs: add documentation for ADMIN ALTER DDL JOBS command #19492

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1 change: 1 addition & 0 deletions TOC.md
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- SQL Statements
- [Overview](/sql-statements/sql-statement-overview.md)
- [`ADMIN`](/sql-statements/sql-statement-admin.md)
- [`ADMIN ALTER DDL JOBS`](/sql-statements/sql-statement-admin-alter-ddl.md)
- [`ADMIN CANCEL DDL`](/sql-statements/sql-statement-admin-cancel-ddl.md)
- [`ADMIN CHECKSUM TABLE`](/sql-statements/sql-statement-admin-checksum-table.md)
- [`ADMIN CHECK [TABLE|INDEX]`](/sql-statements/sql-statement-admin-check-table-index.md)
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83 changes: 83 additions & 0 deletions sql-statements/sql-statement-admin-alter-ddl.md
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---
title: ADMIN ALTER DDL JOBS
summary: An overview of the usage of `ADMIN ALTER DDL JOBS` for the TiDB database.
---

# ADMIN ALTER DDL JOBS

`ADMIN ALTER DDL JOBS` can be used to change the parameter of a running DDL job. For example:
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```sql
ADMIN ALTER DDL JOBS 101 THREAD = 8;
```

- `101`: indicates the ID of the DDL job. You can obtain the ID by executing [`ADMIN SHOW DDL JOBS`](/sql-statements/sql-statement-admin-show-ddl.md).
- `THREAD`: indicates the concurrency of the DDL job. You can configure the initial value of the thread by the system variable [`tidb_ddl_reorg_worker_cnt`](/system-variables.md#tidb_ddl_reorg_worker_cnt).

The following DDL job types support `ADMIN ALTER DDL JOBS`: `ADD INDEX`, `MODIFY COLUMN`, and `REORGANIZE PARTITION`. For other DDL job types, executing `ADMIN ALTER DDL JOBS` reports an error `unsupported DDL operation`.

Currently, you can only modiy the parameters of a single DDL job by executing `ADMIN ALTER DDL JOBS`. Modifying the parameters of multiple IDs at the same time is not supported.

The following are the supported parameters for different DDL jobs and their corresponding system variables:

- `ADD INDEX`:
- `THREAD`: the concurrency of the DDL job. The initial value is set by `tidb_ddl_reorg_worker_cnt`.
- `BATCH_SIZE`: the batch size. The initial value is set by [`tidb_ddl_reorg_batch_size`](/system-variables.md#tidb_ddl_reorg_batch_size).
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- `MAX_WRITE_SPEED`: the maximum bandwidth limit for importing index records into each TiKV. The initial value is set by [`tidb_ddl_reorg_max_write_speed`](/system-variables.md#tidb_ddl_reorg_max_write_speed).
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- `MODIFY COLUMN`:
- `THREAD`: the concurrency of the DDL job. The initial value is set by `tidb_ddl_reorg_worker_cnt`.
- `BATCH_SIZE`: the batch size. The initial value is set by `tidb_ddl_reorg_batch_size`.

- `REORGANIZE PARTITION`:
- `THREAD`: the concurrency of the DDL job. The initial value is set by `tidb_ddl_reorg_worker_cnt`.
- `BATCH_SIZE`: the batch size. The initial value is set by `tidb_ddl_reorg_batch_size`.

The value range of the parameter is consistent with that of the system variable.

`ADMIN ALTER DDL JOBS` takes effect only for running DDL jobs. If the DDL job does not exist or has ended, execution of this statement results in a `ddl job is not running` error.

The following are examples of this statement:

```sql
ADMIN ALTER DDL JOBS 101 THREAD = 8;
ADMIN ALTER DDL JOBS 101 BATCH_SIZE = 256;
ADMIN ALTER DDL JOBS 101 MAX_WRITE_SPEED = '200MiB';
ADMIN ALTER DDL JOBS 101 THREAD = 8, BATCH_SIZE = 256;
```

To view the current parameter values for a particular DDL job, you can execute `ADMIN SHOW DDL JOBS` and the results are displayed in the `COMMENTS` column:
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```sql
mysql> ADMIN SHOW DDL JOBS 1;
+--------+---------+------------+-----------+--------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+--------+-----------------------+
| JOB_ID | DB_NAME | TABLE_NAME | JOB_TYPE | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME | START_TIME | END_TIME | STATE | COMMENTS |
+--------+---------+------------+-----------+--------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+--------+-----------------------+
| 124 | test | t | add index | public | 2 | 122 | 3 | 2024-11-15 11:17:06.213000 | 2024-11-15 11:17:06.213000 | 2024-11-15 11:17:08.363000 | synced | ingest, DXF, thread=8 |
+--------+---------+------------+-----------+--------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+--------+-----------------------+
1 row in set (0.01 sec)
```

## Synopsis

```ebnf+diagram
AdminAlterDDLStmt ::=
'ADMIN' 'ALTER' 'DDL' 'JOBS' Int64Num AlterJobOptionList

AlterJobOptionList ::=
AlterJobOption ( ',' AlterJobOption )*

AlterJobOption ::=
identifier "=" SignedLiteral
```

## MySQL compatibility

`ADMIN ALTER DDL JOBS` statement is a TiDB extension to MySQL syntax.
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## See also

* [`ADMIN SHOW DDL [JOBS|QUERIES]`](/sql-statements/sql-statement-admin-show-ddl.md)
* [`ADMIN CANCEL DDL`](/sql-statements/sql-statement-admin-cancel-ddl.md)
* [`ADMIN PAUSE DDL`](/sql-statements/sql-statement-admin-pause-ddl.md)
* [`ADMIN RESUME DDL`](/sql-statements/sql-statement-admin-resume-ddl.md)
56 changes: 32 additions & 24 deletions sql-statements/sql-statement-admin-show-ddl.md
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### `ADMIN SHOW DDL JOBS`

The `ADMIN SHOW DDL JOBS` statement is used to view all the results in the current DDL job queue, including running and queuing tasks, as well as the latest ten results in the completed DDL job queue. The returned result fields are described as follows:
The `ADMIN SHOW DDL JOBS` statement is used to view all the results in the current DDL job queue, including running and queuing tasks, as well as the recent results in the completed DDL job queue. The returned result fields are described as follows:
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<CustomContent platform="tidb">

Expand All @@ -66,9 +66,7 @@
- `create schema`: for [`CREATE SCHEMA`](/sql-statements/sql-statement-create-database.md) operations.
- `create table`: for [`CREATE TABLE`](/sql-statements/sql-statement-create-table.md) operations.
- `create view`: for [`CREATE VIEW`](/sql-statements/sql-statement-create-view.md) operations.
- `ingest`: ingestion with accelerated index backfilling as configured by [`tidb_ddl_enable_fast_reorg`](/system-variables.md#tidb_ddl_enable_fast_reorg-new-in-v630).
- `txn`: basic transactional backfilling.
- `add index /* txn-merge */`: transactional backfilling with a temporary index that gets merged with the original index when the backfilling is finished.
- `add index`: for [`ADD INDEX`](/sql-statements/sql-statement-add-index.md) operations.
- `SCHEMA_STATE`: the current state of the schema object that the DDL operates on. If `JOB_TYPE` is `ADD INDEX`, it is the state of the index; if `JOB_TYPE` is `ADD COLUMN`, it is the state of the column; if `JOB_TYPE` is `CREATE TABLE`, it is the state of the table. Common states include the following:
- `none`: indicates that it does not exist. Generally, after the `DROP` operation or after the `CREATE` operation fails and rolls back, it will become the `none` state.
- `delete only`, `write only`, `delete reorganization`, `write reorganization`: these four states are intermediate states. For their specific meanings, see [How the Online DDL Asynchronous Change Works in TiDB](/ddl-introduction.md#how-the-online-ddl-asynchronous-change-works-in-tidb). As the intermediate state conversion is fast, these states are generally not visible during operation. Only when performing `ADD INDEX` operation can the `write reorganization` state be seen, indicating that index data is being added.
Expand All @@ -91,6 +89,15 @@
- `pausing`: indicates that the operation is being paused.
- `paused`: indicates that the operation has been paused. This state only appears when you use the [`ADMIN PAUSED DDL JOBS`](/sql-statements/sql-statement-admin-pause-ddl.md) command to pause the DDL job. You can use the [`ADMIN RESUME DDL JOBS`](/sql-statements/sql-statement-admin-resume-ddl.md) command to resume the DDL job.
- `done`: indicates that the operation has been successfully executed on the TiDB owner node, but other TiDB nodes have not yet synchronized the changes performed by this DDL job.
- `COMMENTS`: contains other information for auxiliary diagnostic purposes.
- `ingest`: ingest task for accelerated adding index backfill configured via [`tidb_ddl_enable_fast_reorg`](/system-variables.md#tidb_ddl_enable_fast_reorg-new-in-v630)。

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{"message": "[PingCAP.ZhPunctuation] Don't use Chinese punctuation (。) in English text.", "location": {"path": "sql-statements/sql-statement-admin-show-ddl.md", "range": {"start": {"line": 93, "column": 173}}}, "severity": "ERROR"}
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- `txn`: basic transactional backfill.
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- `txn-merge`: transactional backfilling with a temporary index that gets merged with the original index when the backfilling is finished.
- `DXF`: tasks executed with distributed frameworks configured via [`tidb_enable_dist_task`](/system-variables.md#tidb_enable_dist_task-new-in-v710).
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- `service_scope`: the service scope of the TiDB node configured via [`tidb_service_scope`](/system-variables.md#tidb_service_scope-new-in-v740).
- `thread`: concurrency of backfill tasks. The initial value can be set with `tidb_ddl_reorg_worker_cnt`. It supports dynamic modification via [`ADMIN ALTER DDL JOBS`](/sql-statements/sql-statement-admin-alter-ddl.md).
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- `batch_size`: batch size of backfill tasks. The initial value can be set with `tidb_ddl_reorg_batch_size`. It supports dynamic modification via `ADMIN ALTER DDL JOBS`.
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- `max_write_speed`: flow control during ingest task import. The initial value can be set with `tidb_ddl_reorg_max_write_speed`. It supports dynamic modification via `ADMIN ALTER DDL JOBS`.

</CustomContent>

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```

```sql
mysql> ADMIN SHOW DDL JOBS;
+--------+---------+--------------------+--------------+----------------------+-----------+----------+-----------+-----------------------------------------------------------------+---------+
| JOB_ID | DB_NAME | TABLE_NAME | JOB_TYPE | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME | START_TIME | END_TIME | STATE |
+--------+---------+--------------------+--------------+----------------------+-----------+----------+-----------+---------------------+-------------------------------------------+---------+
| 59 | test | t1 | add index | write reorganization | 1 | 55 | 88576 | 2020-08-17 07:51:58 | 2020-08-17 07:51:58 | NULL | running |
| 60 | test | t2 | add index | none | 1 | 57 | 0 | 2020-08-17 07:51:59 | 2020-08-17 07:51:59 | NULL | none |
| 58 | test | t2 | create table | public | 1 | 57 | 0 | 2020-08-17 07:41:28 | 2020-08-17 07:41:28 | 2020-08-17 07:41:28 | synced |
| 56 | test | t1 | create table | public | 1 | 55 | 0 | 2020-08-17 07:41:02 | 2020-08-17 07:41:02 | 2020-08-17 07:41:02 | synced |
| 54 | test | t1 | drop table | none | 1 | 50 | 0 | 2020-08-17 07:41:02 | 2020-08-17 07:41:02 | 2020-08-17 07:41:02 | synced |
| 53 | test | t1 | drop index | none | 1 | 50 | 0 | 2020-08-17 07:35:44 | 2020-08-17 07:35:44 | 2020-08-17 07:35:44 | synced |
| 52 | test | t1 | add index | public | 1 | 50 | 451010 | 2020-08-17 07:34:43 | 2020-08-17 07:34:43 | 2020-08-17 07:35:16 | synced |
| 51 | test | t1 | create table | public | 1 | 50 | 0 | 2020-08-17 07:34:02 | 2020-08-17 07:34:02 | 2020-08-17 07:34:02 | synced |
| 49 | test | t1 | drop table | none | 1 | 47 | 0 | 2020-08-17 07:34:02 | 2020-08-17 07:34:02 | 2020-08-17 07:34:02 | synced |
| 48 | test | t1 | create table | public | 1 | 47 | 0 | 2020-08-17 07:33:37 | 2020-08-17 07:33:37 | 2020-08-17 07:33:37 | synced |
| 46 | mysql | stats_extended | create table | public | 3 | 45 | 0 | 2020-08-17 06:42:38 | 2020-08-17 06:42:38 | 2020-08-17 06:42:38 | synced |
| 44 | mysql | opt_rule_blacklist | create table | public | 3 | 43 | 0 | 2020-08-17 06:42:38 | 2020-08-17 06:42:38 | 2020-08-17 06:42:38 | synced |
+--------+---------+--------------------+--------------+----------------------+-----------+----------+-----------+---------------------+---------------------+-------------------------------+
12 rows in set (0.00 sec)
+--------+---------+------------+---------------------------------+----------------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+----------+-------------+
| JOB_ID | DB_NAME | TABLE_NAME | JOB_TYPE | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME | START_TIME | END_TIME | STATE | COMMENTS |
+--------+---------+------------+---------------------------------+----------------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+----------+-------------+
| 565 | test | sbtest1 | add index | write reorganization | 554 | 556 | 0 | 2024-11-22 12:39:25.475000 | 2024-11-22 12:39:25.524000 | NULL | running | ingest, DXF |
| 566 | test | sbtest1 | add index | none | 554 | 556 | 0 | 2024-11-22 12:39:26.425000 | NULL | NULL | queueing | |
| 564 | test | sbtest1 | alter table multi-schema change | none | 554 | 556 | 0 | 2024-11-22 12:39:02.925000 | 2024-11-22 12:39:02.925000 | 2024-11-22 12:39:03.275000 | synced | |
| 564 | test | sbtest1 | drop index /* subjob */ | none | 554 | 556 | 0 | 2024-11-22 12:39:02.925000 | 2024-11-22 12:39:02.925000 | 2024-11-22 12:39:03.275000 | done | |
| 564 | test | sbtest1 | drop index /* subjob */ | none | 554 | 556 | 0 | 2024-11-22 12:39:02.925000 | 2024-11-22 12:39:02.975000 | 2024-11-22 12:39:03.275000 | done | |
| 563 | test | sbtest1 | modify column | public | 554 | 556 | 0 | 2024-11-22 12:38:35.624000 | 2024-11-22 12:38:35.624000 | 2024-11-22 12:38:35.674000 | synced | |
| 562 | test | sbtest1 | add index | public | 554 | 556 | 1580334 | 2024-11-22 12:36:58.471000 | 2024-11-22 12:37:05.271000 | 2024-11-22 12:37:13.374000 | synced | ingest, DXF |
| 561 | test | sbtest1 | add index | public | 554 | 556 | 1580334 | 2024-11-22 12:36:57.771000 | 2024-11-22 12:36:57.771000 | 2024-11-22 12:37:04.671000 | synced | ingest, DXF |
| 560 | test | sbtest1 | add index | public | 554 | 556 | 1580334 | 2024-11-22 12:34:53.314000 | 2024-11-22 12:34:53.314000 | 2024-11-22 12:34:57.114000 | synced | ingest |
| 559 | test | sbtest1 | drop index | none | 554 | 556 | 0 | 2024-11-22 12:34:43.565000 | 2024-11-22 12:34:43.565000 | 2024-11-22 12:34:43.764000 | synced | |
| 558 | test | sbtest1 | add index | public | 554 | 556 | 1580334 | 2024-11-22 12:34:06.215000 | 2024-11-22 12:34:06.215000 | 2024-11-22 12:34:14.314000 | synced | ingest, DXF |
| 557 | test | sbtest1 | create table | public | 554 | 556 | 0 | 2024-11-22 12:32:09.515000 | 2024-11-22 12:32:09.915000 | 2024-11-22 12:32:10.015000 | synced | |
| 555 | test | | create schema | public | 554 | 0 | 0 | 2024-11-22 12:31:51.215000 | 2024-11-22 12:31:51.264000 | 2024-11-22 12:31:51.264000 | synced | |
| 553 | test | | drop schema | none | 2 | 0 | 0 | 2024-11-22 12:31:48.615000 | 2024-11-22 12:31:48.615000 | 2024-11-22 12:31:48.865000 | synced | |
+--------+---------+------------+---------------------------------+----------------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+----------+-------------+
14 rows in set (0.00 sec)
```

From the output above:

- Job 59 is currently in progress (`STATE` of `running`). The schema state is currently in `write reorganization`, but will switch to `public` once the task is completed to note that the change can be observed publicly by user sessions. The `end_time` column is also `NULL` indicating that the completion time for the job is currently not known.
- Job 565 is currently in progress (`STATE` of `running`). The schema state is currently in `write reorganization`, but will switch to `public` once the task is completed to note that the change can be observed publicly by user sessions. The `end_time` column is also `NULL` indicating that the completion time for the job is currently not known.
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- Job 60 is an `add index` job, which is currently queued waiting for job 59 to complete. When job 59 completes, the `STATE` of job 60 will switch to `running`.
- The `STATE` for `job_id` 566 is shown as `queueing`, indicating that it is queuing. When job 565 completes and job 566 begins execution, the `STATE` for job 566 will change to `running`.

- For destructive changes such as dropping an index or dropping a table, the `SCHEMA_STATE` will change to `none` when the job is complete. For additive changes, the `SCHEMA_STATE` will change to `public`.

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