distribute-table: support to scatter the region distribution of the given table and engine

sql-statements/sql_statement_distribute_table.md

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+---
+title: distribute table 使用文档
+aliases: ['/docs-cn/dev/sql-statements/sql-statement-distribute-table/','/docs-cn/dev/reference/sql/statements/distribute-table/']
+summary: TiDB 中的 distribute table 功能可以解决表中 region 分布不均衡问题。通过重新调整 table 中的 region 的分布，可以让指定 table 下的 region 按照一定的策略进行均衡。重新分配可以指定不同的存储引擎，比如 TIFLASH 和 TIKV。同时也可以指定不同的 raft role，比如 learner，leader，voter。
+---
+
+# Distribute Table 使用文档
+
+## 语法图
+
+```ebnf+diagram
+DistributeTableStmt ::=
+    "DISTRIBUTE"  "TABLE" TableName PartitionNameList?  EngineOption? RoleOption?
+
+TableName ::=
+    (SchemaName ".")? Identifier
+
+PartitionNameList ::=
+    "PARTITION" "(" PartitionName ("," PartitionName)* ")"
+
+EngineOption ::=
+    "ENGINE" Expression
+
+RoleOption ::=
+    "Role" Expression
+
+```
+
+## 示例
+
+对表A 上的 tikv 上的 leader 重新进行均衡调度
+```sql
+CREATE TABLE t1 (a INT)；
+...
+DISTRIBUTE TABLE table_name engine tikv role leader
+```
++---------+
+| JOB_ID  | 
+100
++---------+
+
+
+
+显示当前所有的调度任务
+```sql
+SHOW DISTRIBUTION JOBS;
+```
+
++---------+------------+------------+-----------------+------------+-----------+----------+-------------+---------------+
+| JOB_ID  |  DB_NAME   | TABLE_NAME | PARTITION_NAMES | ENGINE_TYPE | ROLE_TYPE | STATUS  | CREATE_USER | CREATE_TIME   |
++---------+------------+------------+-----------------+------------+-----------+--------+---------------+---------------+
+|    1    |   db_1     |    t1      |                 | TIKV       | LEADER    | RUNNING  | ADMIN       |   20240712    |
+|    2    |   db_1     |    t2      |                 | TIFLASH    | LEARNER   | FINISHED | ADMIN       | 20240715      |
+|    3    |   db_1     |    t3      |                 | TiKV       | VOTER     | STOPPED  | ADMIN       | 20240713      |
+|    4    |   db_1     |    t4      |                 | TIFLASH    | LEARNER   | FINISHED | ADMIN       | 20240713      |
++---------+------------+------------+-----------------+------------+-----------+----------+-------------+---------------+
+
+
+显示当前表 t1 的 region 分布情况
+```sql
+SHOW TABLE DISTRIBUTION t1;
+```
+
++---------+------------+----------------+----------+------------+-------------------+--------------------+-----------------+------------------+
+| DB_NAME | TABLE_NAME | PARTITION_NAME | STORE_ID | STORE_TYPE | REGION_LEADER_NUM | REGION_LEADER_BYTE | REGION_PEER_NUM | REGION_PEER_BYTE |
++---------+------------+----------------+----------+------------+-------------------+--------------------+-----------------+------------------+
+| db_1    |     t1     |                | 1        | TiKV       |               315 |        24057934521 |            1087 |      86938746542 |
+| db_1    |     t1     |                | 2        | TiKV       |               324 |        28204839240 |            1104 |      91039476832 |
+| db_1    |     t1     |                | 3        | TiKV       |               319 |        25986274812 |            1091 |      89405367423 |
+| db_1    |     t1     |                | 4        | TiKV       |               503 |        41039587625 |            1101 |      90482317797 |
++---------+------------+----------------+----------+------------+-------------------+--------------------+-----------------+------------------+
+
+### Distribute Table Region
+
+
+## 注意事项
+
+Distribute Table 语句重新调度 table 下的 region 也会受到 PD 中热点调度器的影响。 同时该任务会在均衡后退出，退出后该表的分布可能会
+被被破坏。
+
+## MySQL 兼容性
+该语句是 TiDB 对 MySQL 语法的扩展。
+
+## 另请参阅