SHOW TABLE REGIONS

SHOW TABLE REGIONS 语句用于显示 TiDB 中某个表的 Region 信息。

语法

SHOW TABLE [table_name] REGIONS [WhereClauseOptional]; SHOW TABLE [table_name] INDEX [index_name] REGIONS [WhereClauseOptional];

语法图

ShowTableRegionStmt:

ShowTableRegionStmt

TableName:

TableName

PartitionNameListOpt:

PartitionNameListOpt

WhereClauseOptional:

WhereClauseOptional

WhereClause:

WhereClause

SHOW TABLE REGIONS 会返回如下列:

  • REGION_ID:Region 的 ID。
  • START_KEY:Region 的 Start key。
  • END_KEY:Region 的 End key。
  • LEADER_ID:Region 的 Leader ID。
  • LEADER_STORE_ID:Region leader 所在的 store (TiKV) ID。
  • PEERS:Region 所有副本的 ID。
  • SCATTERING:Region 是否正在调度中。1 表示正在调度。
  • WRITTEN_BYTES:估算的 Region 在 1 个心跳周期内的写入数据量大小,单位是 byte。
  • READ_BYTES:估算的 Region 在 1 个心跳周期内的读数据量大小,单位是 byte。
  • APPROXIMATE_SIZE(MB):估算的 Region 的数据量大小,单位是 MB。
  • APPROXIMATE_KEYS:估算的 Region 内 Key 的个数。
  • SCHEDULING_CONSTRAINTS:Region 所在的表或者分区所关联的放置策略的规则。
  • SCHEDULING_STATE:关联了放置策略的 Region 的当前调度状态。

示例

创建一个示例表,并在若干 Region 中填充足够的数据量:

CREATE TABLE t1 ( id INT NOT NULL PRIMARY KEY auto_increment, b INT NOT NULL, pad1 VARBINARY(1024), pad2 VARBINARY(1024), pad3 VARBINARY(1024) ); INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM dual; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; INSERT INTO t1 SELECT NULL, FLOOR(RAND()*1000), RANDOM_BYTES(1024), RANDOM_BYTES(1024), RANDOM_BYTES(1024) FROM t1 a JOIN t1 b JOIN t1 c LIMIT 10000; SELECT SLEEP(5); SHOW TABLE t1 REGIONS;

结果显示示例表被切分成多个 Regions。REGION_IDSTART_KEYEND_KEY 可能不完全匹配:

SHOW TABLE t1 REGIONS;
+-----------+--------------+--------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE | +-----------+--------------+--------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | 94 | t_75_ | t_75_r_31717 | 95 | 1 | 95 | 0 | 0 | 0 | 112 | 207465 | | | | 96 | t_75_r_31717 | t_75_r_63434 | 97 | 1 | 97 | 0 | 0 | 0 | 97 | 0 | | | | 2 | t_75_r_63434 | | 3 | 1 | 3 | 0 | 269323514 | 66346110 | 245 | 162020 | | | +-----------+--------------+--------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ 3 rows in set (0.00 sec)

解释:

上面 START_KEY 列的值 t_75_r_31717END_KEY 列的值 t_75_r_63434 表示主键在 3171763434 之间的数据存储在该 Region 中。t_75_ 是前缀,表示这是表格 (t) 的 Region,75 是表格的内部 ID。若 START_KEYEND_KEY 的一对键值为空,分别表示负无穷大或正无穷大。

TiDB 会根据需要自动重新平衡 Regions。建议使用 SPLIT TABLE REGION 语句手动进行平衡:

SPLIT TABLE t1 BETWEEN (31717) AND (63434) REGIONS 2;
+--------------------+----------------------+ | TOTAL_SPLIT_REGION | SCATTER_FINISH_RATIO | +--------------------+----------------------+ | 1 | 1 | +--------------------+----------------------+ 1 row in set (42.34 sec)
SHOW TABLE t1 REGIONS;
+-----------+--------------+--------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE | +-----------+--------------+--------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | 94 | t_75_ | t_75_r_31717 | 95 | 1 | 95 | 0 | 0 | 0 | 112 | 207465 | | | | 98 | t_75_r_31717 | t_75_r_47575 | 99 | 1 | 99 | 0 | 1325 | 0 | 53 | 12052 | | | | 96 | t_75_r_47575 | t_75_r_63434 | 97 | 1 | 97 | 0 | 1526 | 0 | 48 | 0 | | | | 2 | t_75_r_63434 | | 3 | 1 | 3 | 0 | 0 | 55752049 | 60 | 0 | | | +-----------+--------------+--------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ 4 rows in set (0.00 sec)

上面的输出结果显示 Region 96 被切分,并创建一个新的 Region 98。切分操作不会影响表中的其他 Region。输出结果同样证实:

  • TOTAL_SPLIT_REGION 表示新切的 Region 数量。以上示例新切了 1 个 Region。
  • SCATTER_FINISH_RATIO 表示新切的 Region 的打散成功率,1.0 表示都已经打散了。

更详细的示例如下:

show table t regions;
+-----------+--------------+--------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE | +-----------+--------------+--------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | 102 | t_43_r | t_43_r_20000 | 118 | 7 | 105, 118, 119 | 0 | 0 | 0 | 1 | 0 | | | | 106 | t_43_r_20000 | t_43_r_40000 | 120 | 7 | 107, 108, 120 | 0 | 23 | 0 | 1 | 0 | | | | 110 | t_43_r_40000 | t_43_r_60000 | 112 | 9 | 112, 113, 121 | 0 | 0 | 0 | 1 | 0 | | | | 114 | t_43_r_60000 | t_43_r_80000 | 122 | 7 | 115, 122, 123 | 0 | 35 | 0 | 1 | 0 | | | | 3 | t_43_r_80000 | | 93 | 8 | 5, 73, 93 | 0 | 0 | 0 | 1 | 0 | | | | 98 | t_43_ | t_43_r | 99 | 1 | 99, 100, 101 | 0 | 0 | 0 | 1 | 0 | | | +-----------+--------------+--------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ 6 rows in set

解释:

  • Region 102 的 START_KEYEND_KEY 中,t_43 是表数据前缀和 table ID,_r 是表 t record 数据的前缀,索引数据的前缀是 _i,所以 Region 102 的 START_KEYEND_KEY 表示用来存储 [-inf, 20000) 之前的 record 数据。其他 Region (106, 110, 114, 3) 的存储范围依次类推。
  • Region 98 用来存储索引数据存储。表 t 索引数据的起始 key 是 t_43_i,处于 Region 98 的存储范围内。

查看表 t 在 store 1 上的 region,用 WHERE 条件过滤。

show table t regions where leader_store_id =1;
+-----------+-----------+---------+-----------+-----------------+--------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE | +-----------+-----------+---------+-----------+-----------------+--------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | 98 | t_43_ | t_43_r | 99 | 1 | 99, 100, 101 | 0 | 0 | 0 | 1 | 0 | | | +-----------+-----------+---------+-----------+-----------------+--------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+

SPLIT TABLE REGION 语法切分索引数据的 Region,下面语法把表 t 的索引 name 数据在 [a,z] 范围内切分成 2 个 Region。

split table t index name between ("a") and ("z") regions 2;
+--------------------+----------------------+ | TOTAL_SPLIT_REGION | SCATTER_FINISH_RATIO | +--------------------+----------------------+ | 2 | 1.0 | +--------------------+----------------------+ 1 row in set

现在表 t 一共有 7 个 Region,其中 5 个 Region (102, 106, 110, 114, 3) 用来存表 t 的 record 数据,另外 2 个 Region (135, 98) 用来存 name 索引的数据。

show table t regions;
+-----------+-----------------------------+-----------------------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE | +-----------+-----------------------------+-----------------------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ | 102 | t_43_r | t_43_r_20000 | 118 | 7 | 105, 118, 119 | 0 | 0 | 0 | 1 | 0 | | | | 106 | t_43_r_20000 | t_43_r_40000 | 120 | 7 | 108, 120, 126 | 0 | 0 | 0 | 1 | 0 | | | | 110 | t_43_r_40000 | t_43_r_60000 | 112 | 9 | 112, 113, 121 | 0 | 0 | 0 | 1 | 0 | | | | 114 | t_43_r_60000 | t_43_r_80000 | 122 | 7 | 115, 122, 123 | 0 | 35 | 0 | 1 | 0 | | | | 3 | t_43_r_80000 | | 93 | 8 | 73, 93, 128 | 0 | 0 | 0 | 1 | 0 | | | | 135 | t_43_i_1_ | t_43_i_1_016d80000000000000 | 139 | 2 | 138, 139, 140 | 0 | 35 | 0 | 1 | 0 | | | | 98 | t_43_i_1_016d80000000000000 | t_43_r | 99 | 1 | 99, 100, 101 | 0 | 0 | 0 | 1 | 0 | | | +-----------+-----------------------------+-----------------------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+ 7 rows in set

MySQL 兼容性

SHOW TABLE REGIONS 语句是 TiDB 对 MySQL 语法的扩展。

另请参阅

文档内容是否有帮助?

下载 PDF文档反馈社区交流
产品
TiDB
TiDB Cloud
© 2024 PingCAP. All Rights Reserved.
Privacy Policy.