SHOW TABLE REGIONS

The SHOW TABLE REGIONS statement is used to show the Region information of a table in TiDB.

Synopsis

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

Executing SHOW TABLE REGIONS returns the following columns:

REGION_ID: The Region ID.
START_KEY: The start key of the Region.
END_KEY: The end key of the Region.
LEADER_ID: The Leader ID of the Region.
LEADER_STORE_ID: The ID of the store (TiKV) where the Region leader is located.
PEERS: The IDs of all Region replicas.
SCATTERING: Whether the Region is being scheduled. 1 means true.
WRITTEN_BYTES: The estimated amount of data written into the Region within one heartbeat cycle. The unit is byte.
READ_BYTES: The estimated amount of data read from the Region within one heartbeat cycle. The unit is byte.
APPROXIMATE_SIZE(MB): The estimated amount of data in the Region. The unit is megabytes (MB).
APPROXIMATE_KEYS: The estimated number of Keys in the Region.

Note:

The values of WRITTEN_BYTES, READ_BYTES, APPROXIMATE_SIZE(MB), APPROXIMATE_KEYS are not accurate data. They are estimated data from PD based on the heartbeat information that PD receives from the Region.

Examples

test> create table t (id int key,name varchar(50), index (name));
Query OK, 0 rows affected

After a table is created, the table data is stored in a newly split Region by default. In this initial phase, all row data and index data of the table are written into this Region.

test> 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 |
+-----------+-----------+---------+-----------+-----------------+-----------+------------+---------------+------------+----------------------+------------------+
| 3         | t_43_     |         | 73        | 9               | 5, 73, 93 | 0          | 35            | 0          | 1                    | 0                |
+-----------+-----------+---------+-----------+-----------------+-----------+------------+---------------+------------+----------------------+------------------+
1 row in set

In the above result, t_43_ is the value of START_KEY row. In this value, t is the table prefix and 43 is the table ID. The value of END_KEY row is empty (""), which means that it is an infinite value.

Use the SPLIT TABLE REGION statement to split row data into five Regions.

test> split table t between (0) and (100000) regions 5;
+--------------------+----------------------+
| TOTAL_SPLIT_REGION | SCATTER_FINISH_RATIO |
+--------------------+----------------------+
| 5                  | 1.0                  |
+--------------------+----------------------+

In the above example:

TOTAL_SPLIT_REGION indicates the number of newly split Regions. In this example, the number is 5.
SCATTER_FINISH_RATIO indicates the rate at which the newly split Regions are successfully scattered. 1.0 means that all Regions are scattered.

test> 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 |
+-----------+--------------+--------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+
| 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

In the above example:

Table t corresponds to six Regions. In these Regions, 102, 106, 110, 114, and 3 store the row data and 98 stores the index data.
For START_KEY and END_KEY of Region 102, t_43 indicates the table prefix and ID. _r is the prefix of the record data in table t. _i is the prefix of the index data.
In Region 102, START_KEY and END_KEY mean that record data in the range of [-inf, 20000) is stored. In similar way, the ranges of data storage in Regions (103, 109, 113, 2) can also be calculated.
Region 98 stores the index data. The start key of table t's index data is t_43_i, which is in the range of Region 98.

To check the Region that corresponds to table t in store 1, use the WHERE clause:

test> 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 |
+-----------+-----------+---------+-----------+-----------------+--------------+------------+---------------+------------+----------------------+------------------+
| 98        | t_43_     | t_43_r  | 99        | 1               | 99, 100, 101 | 0          | 0             | 0          | 1                    | 0                |
+-----------+-----------+---------+-----------+-----------------+--------------+------------+---------------+------------+----------------------+------------------+

Use SPLIT TABLE REGION to split the index data into Regions. In the following example, the index data name of table t is split into two Regions in the range of [a,z].

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

Now table t corresponds to seven Regions. Five of them (102, 106, 110, 114, 3) store the record data of table t and another two (135, 98) store the index data name.

test> 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 |
+-----------+-----------------------------+-----------------------------+-----------+-----------------+---------------+------------+---------------+------------+----------------------+------------------+
| 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

SHOW TABLE REGIONS

Synopsis

Examples

See also