docs: adds region_statistics refernece

docs/reference/sql/information-schema/overview.md

@@ -52,6 +52,7 @@ There is still lots of work to do for `INFORMATION_SCHEMA`. The tracking [issue]
 | --- | --- |
 | [`BUILD_INFO`](./build-info.md) | Provides the system build info. |
 | [`REGION_PEERS`](./region-peers.md) | Provides details about where regions are stored. |
+| [`REGION_STATISTICS`](./region-statistics.md) | Provides details about region statistics info, such as disk size, etc. |
 | [`RUNTIME_METRICS`](./runtime-metrics.md)| Provides the system runtime metrics.|
 | [`CLUSTER_INFO`](./cluster-info.md)| Provides the topology information of the cluster.|
 | [`FLOWS`](./flows.md) | Provides the flow information.|

docs/reference/sql/information-schema/region-statistics.md

@@ -0,0 +1,63 @@
+# REGION_STATISTICS
+
+The `REGION_STATISTICS` table provides detailed information about a region's statistics, including the total number of rows, disk size, and more. These statistics are approximate values.
+
+:::tip NOTE
+This table is not available on [GreptimeCloud](https://greptime.cloud/).
+:::
+
+```sql
+USE INFORMATION_SCHEMA;
+DESC REGION_STATISTICS;
+```
+
+The output is as follows:
+
+```sql
++---------------+--------+------+------+---------+---------------+
+| Column        | Type   | Key  | Null | Default | Semantic Type |
++---------------+--------+------+------+---------+---------------+
+| region_id     | UInt64 |      | NO   |         | FIELD         |
+| table_id      | UInt32 |      | NO   |         | FIELD         |
+| region_number | UInt32 |      | NO   |         | FIELD         |
+| region_rows   | UInt64 |      | YES  |         | FIELD         |
+| disk_size     | UInt64 |      | YES  |         | FIELD         |
+| memtable_size | UInt64 |      | YES  |         | FIELD         |
+| manifest_size | UInt64 |      | YES  |         | FIELD         |
+| sst_size      | UInt64 |      | YES  |         | FIELD         |
+| index_size    | UInt64 |      | YES  |         | FIELD         |
+| engine        | String |      | YES  |         | FIELD         |
+| region_role   | String |      | YES  |         | FIELD         |
++---------------+--------+------+------+---------+---------------+
+```
+
+Fields in the `REGION_STATISTICS` table are described as follows:
+
+- `region_id`: The ID of the Region.
+- `table_id`: The ID of the table.
+- `region_number`: The number of the region in the table.
+- `region_rows`:  The number of rows in the region.
+- `disk_size`:  The total size of data files in the region, including data, index and metadata etc.
+- `memtable_size`: The region's total size of memtables.
+- `manifest_size`: The region's total size of manifest files.
+- `sst_size`: The region's total size of SST files.
+- `index_size`: The region's total size of index files.
+- `engine`: The engine type of the region, `mito` or `metric`.
+- `region_role`: The region's role, `Leader` or `Follower`.
+
+
+Retrieve a table's region statistics information as follows:
+
+```sql
+SELECT r.* FROM REGION_STATISTICS r LEFT JOIN TABLES t on r.table_id = t.table_id WHERE t.table_name = 'system_metrics';
+```
+
+
+Output:
+```sql
++---------------+----------+---------------+-------------+-----------+---------------+---------------+----------+------------+--------+-------------+
+| region_id     | table_id | region_number | region_rows | disk_size | memtable_size | manifest_size | sst_size | index_size | engine | region_role |
++---------------+----------+---------------+-------------+-----------+---------------+---------------+----------+------------+--------+-------------+
+| 4398046511104 |     1024 |             0 |           8 |      4922 |             0 |          1338 |     3249 |        335 | mito   | Leader      |
++---------------+----------+---------------+-------------+-----------+---------------+---------------+----------+------------+--------+-------------+
+```

docs/reference/sql/information-schema/tables.md

@@ -95,8 +95,12 @@ The description of columns in the `TABLES` table is as follows:
   - `TEMPORARY` for a temporary result set.
   - `VIEW`  for a view.
 - `table_id`: The ID of the table.
+- `data_length`: The total length of the table's SST files in bytes, which is an approximate value.
+- `index_length`: The total length of the table's index files in bytes, which is an approximate value.
+- `table_rows`: The table's total row number, which is an approximate value.
+- `avg_row_length`: The average row length in bytes, which is an approximate value.
 - `engine`: The storage engine of the table used.
 - `version`:  Version. The value is `11` by default.
 - `create_time`: The table created timestamp.
 - `table_comment`: The table comment.
-- Other columns such as `table_rows`, `row_format` etc. are not supported, just for compatibility with MySQL. GreptimeDB may support some of them in the future.
+- Other columns such as `auto_increment`, `row_format` etc. are not supported, just for compatibility with MySQL. GreptimeDB may support some of them in the future.

i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/information-schema/overview.md

@@ -50,6 +50,7 @@
 | --- | --- |
 | [`BUILD_INFO`](./build-info.md) | 提供了系统构建的信息。 |
 | [`REGION_PEERS`](./region-peers.md) | 提供了表的 Region 存储的详细信息。 |
+| [`REGION_STATISTICS`](./region-statistics.md) | 提供 Region 的详细统计信息，例如行数等。 |
 | [`RUNTIME_METRICS`](./runtime-metrics.md)| 提供了系统运行时指标。|
 | [`CLUSTER_INFO`](./cluster-info.md)| 提供了集群的节点拓扑信息。|
 | [`FLOWS`](./flows.md) | 提供 Flow 相关信息。|

i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/information-schema/region-statistics.md

@@ -0,0 +1,62 @@
+# REGION_STATISTICS
+
+`REGION_STATISTICS` 表提供了关于某个 Region 统计信息的详细数据，包括总行数、磁盘大小等。这些统计信息都是近似值。
+
+:::tip NOTE
+此表在 [GreptimeCloud](https://greptime.cloud/) 中不可用。
+:::
+
+```sql
+USE INFORMATION_SCHEMA;
+DESC REGION_STATISTICS;
+```
+
+输出如下：
+
+```sql
++---------------+--------+------+------+---------+---------------+
+| Column        | Type   | Key  | Null | Default | Semantic Type |
++---------------+--------+------+------+---------+---------------+
+| region_id     | UInt64 |      | NO   |         | FIELD         |
+| table_id      | UInt32 |      | NO   |         | FIELD         |
+| region_number | UInt32 |      | NO   |         | FIELD         |
+| region_rows   | UInt64 |      | YES  |         | FIELD         |
+| disk_size     | UInt64 |      | YES  |         | FIELD         |
+| memtable_size | UInt64 |      | YES  |         | FIELD         |
+| manifest_size | UInt64 |      | YES  |         | FIELD         |
+| sst_size      | UInt64 |      | YES  |         | FIELD         |
+| index_size    | UInt64 |      | YES  |         | FIELD         |
+| engine        | String |      | YES  |         | FIELD         |
+| region_role   | String |      | YES  |         | FIELD         |
++---------------+--------+------+------+---------+---------------+
+```
+
+`REGION_STATISTICS` 表中的字段描述如下：
+
+- `region_id`: Region 的 ID。
+- `table_id`: 表的 ID。
+- `region_number`: Region 在表中的编号。
+- `region_rows`: Region 中的记录行数。
+- `disk_size`: Region 中数据文件的总大小，包括数据、索引及元信息等。
+- `memtable_size`: Region 中内存 memtables 的总大小。
+- `manifest_size`: Region 中元信息 manifest 文件的总大小。
+- `sst_size`: Region 中 SST 文件的总大小。
+- `index_size`: Region 中索引文件的总大小。
+- `engine`: Region 的引擎类型，可以是 `mito` 或 `metric`。
+- `region_role`: Region 的角色，可以是 `Leader` 或 `Follower`。
+
+获取某张表的 Region 统计信息如下：
+
+```sql
+SELECT r.* FROM REGION_STATISTICS r LEFT JOIN TABLES t on r.table_id = t.table_id WHERE t.table_name = 'system_metrics';
+```
+
+输出：
+```sql
++---------------+----------+---------------+-------------+-----------+---------------+---------------+----------+------------+--------+-------------+
+| region_id     | table_id | region_number | region_rows | disk_size | memtable_size | manifest_size | sst_size | index_size | engine | region_role |
++---------------+----------+---------------+-------------+-----------+---------------+---------------+----------+------------+--------+-------------+
+| 4398046511104 |     1024 |             0 |           8 |      4922 |             0 |          1338 |     3249 |        335 | mito   | Leader      |
++---------------+----------+---------------+-------------+-----------+---------------+---------------+----------+------------+--------+-------------+
+```
+```

i18n/zh/docusaurus-plugin-content-docs/current/reference/sql/information-schema/tables.md

@@ -96,6 +96,10 @@ SHOW TABLES
   - `TEMPORARY`：临时结果集
   - `VIEW`：视图表
 - `table_id`：表 ID。
+- `data_length`: 表中 SST 文件的总长度（以字节为单位），近似值。
+- `index_length`: 表中索引文件的总长度（以字节为单位），近似值。
+- `table_rows`: 表中总的记录行数，近似值。
+- `avg_row_length`: 表中记录的平均大小（以字节为单位），近似值。
 - `engine`：该表使用的存储引擎。
 - `version`: 版本。固定值为 `11`。
 - `create_time`: 表创建的时间戳。

sidebars.ts

@@ -322,7 +322,7 @@ const sidebars: SidebarsConfig = {
           items: ['enterprise/deployments/authentication',],
         },
         {
-          type: 'category', 
+          type: 'category',
           label: 'Administration',
           items: [
             {
@@ -393,6 +393,7 @@ const sidebars: SidebarsConfig = {
                 'reference/sql/information-schema/views',
                 'reference/sql/information-schema/flows',
                 'reference/sql/information-schema/region-peers',
+                'reference/sql/information-schema/region-statistics',
                 'reference/sql/information-schema/runtime-metrics',
                 'reference/sql/information-schema/cluster-info',
               ],