fix: partitions (#965)

Co-authored-by: tison <wander4096@gmail.com>

docs/nightly/en/reference/sql/functions.md

@@ -42,7 +42,7 @@ Please refer to [API documentation](https://greptimedb.rs/script/python/rspython
 GreptimeDB provides some administration functions to manage the database and data:
 
 * `flush_table(table_name)` to flush a table's memtables into SST file by table name.
-* `flush_region(region_id)` to flush a region's memtables into SST file by region id. Find the region id through [REGION_PEERS](./information-schema/region-peers.md) table.
+* `flush_region(region_id)` to flush a region's memtables into SST file by region id. Find the region id through [PARTITIONS](./information-schema/partitions.md) table.
 * `compact_table(table_name)` to schedule a compaction task for a table by table name.
 * `compact_region(region_id)` to schedule a compaction task for a region by region id.
 * `migrate_region(region_id, from_peer, to_peer, [timeout])` to migrate regions between datanodes, please read the [Region Migration](/user-guide/operations/region-migration).

docs/nightly/en/reference/sql/information-schema/partitions.md

@@ -43,6 +43,19 @@ The output is as follows:
 26 rows in set (0.01 sec)
 ```
 
+Main columns:
+* `table_catalog`: The name of the catalog to which the table belongs. This value is always `def`.
+* `table_schema`: The name of the schema (database) to which the table belongs.
+* `table_name`: The name of the table containing the partition(region).
+* `partition_name`: The name of the partition(region).
+* `partition_ordinal_position`: All partitions are indexed in the same order as they are defined, with 1 being the number assigned to the first partition. 
+* `partition_method`: This value is always `RANGE`, GreptimeDB only supports range partitioning.
+* `partition_expression`: The expression of this partition.
+* `create_time`: The time that the partition was created.
+* `greptime_partition_id`: GreptimeDB extended field, it's the Region Id.
+
+For example, create a partitioned table:
+
 ```sql
 CREATE TABLE public.test_p (
  a INT PRIMARY KEY,
@@ -54,9 +67,13 @@ PARTITION ON COLUMNS (a) (
  a > 10 AND a < 20,
  a >= 20
 );
+
+--- Query the partitions of the table --
 SELECT * FROM PARTITIONS WHERE table_schema='public' AND table_name='test_p'\G
 ```
 
+Outputs:
+
 ```sql
 *************************** 1. row ***************************
  table_catalog: greptime

docs/nightly/en/user-guide/operations/admin.md

@@ -12,7 +12,24 @@ This document addresses strategies and practices used in the operation of Grepti
 ### Runtime information
 
 * Find the topology information of the cluster though [CLUSTER_INFO](/reference/sql/information-schema/cluster-info.md) table.
-* Find the table regions distribution though [REGION_PEERS](/reference/sql/information-schema/region-peers.md) table.
+* Find the table regions distribution though [PARTITIONS](/reference/sql/information-schema/partitions.md) and [REGION_PEERS](/reference/sql/information-schema/region-peers.md) tables.
+
+For example, find all the region id of a table:
+
+```sql
+SELECT greptime_partition_id FROM PARTITIONS WHERE table_name = 'monitor'
+```
+
+Find the distribution of all regions in a table:
+
+```sql
+SELECT b.peer_id as datanode_id,
+ a.greptime_partition_id as region_id
+FROM information_schema.partitions a LEFT JOIN information_schema.region_peers b
+ON a.greptime_partition_id = b.region_id
+WHERE a.table_name='monitor'
+ORDER BY datanode_id ASC
+```
 
 The `INFORMATION_SCHEMA` database provides access to system metadata, such as the name of a database or table, the data type of a column, etc. Please read the [reference](/reference/sql/information-schema/overview.md).
 

docs/nightly/zh/reference/sql/functions.md

@@ -41,7 +41,7 @@ arrow_cast(expression, datatype)
 GreptimeDB 提供了一些管理函数来管理数据库和数据：
 
 * `flush_table(table_name)` 通过表名将表的内存表刷写到 SST 文件。
-* `flush_region(region_id)` 通过 Region Id 将 Region 的内存表刷写到 SST 文件。可以通过 [REGION_PEERS](./information-schema/region-peers.md) 表查找 Region Id。
+* `flush_region(region_id)` 通过 Region Id 将 Region 的内存表刷写到 SST 文件。可以通过 [PARTITIONS](./information-schema/partitions.md) 表查找一张表的所有 Region Id。
 * `compact_table(table_name)` 通过表名为表发起compaction 任务。
 * `compact_region(region_id)` 通过 Region Id 为 Region 发起 compaction 任务。
 * `migrate_region(region_id, from_peer, to_peer, [timeout])` 在 Datanode 之间迁移 Region，请阅读 [ Region迁移](/user-guide/operations/region-migration)。

docs/nightly/zh/reference/sql/information-schema/partitions.md

@@ -43,6 +43,19 @@ DESC PARTITIONS;
 26 rows in set (0.01 sec)
 ```
 
+主要列包括：
+* `table_catalog`：表所属目录的名称。该值始终为 `def`。
+* `table_schema`：表所属的 schema（数据库）的名称。
+* `table_name`：包含分区（region）的表的名称。
+* `partition_name`：分区（region）的名称。
+* `partition_ordinal_position`：所有分区按照定义的顺序进行索引，1 是分配给第一个分区的编号。
+* `partition_method`：该值始终为 `RANGE`，GreptimeDB 仅支持范围分区。
+* `partition_expression`：该分区的表达式。
+* `create_time`：分区创建的时间。
+* `greptime_partition_id`：GreptimeDB 扩展字段，也就是 Region Id。
+
+创建一张分区表并查询：
+
 ```sql
 CREATE TABLE public.test_p (
  a INT PRIMARY KEY,
@@ -54,9 +67,13 @@ PARTITION ON COLUMNS (a) (
  a > 10 AND a < 20,
  a >= 20
 );
+
+--- 查询表的分区信息---
 SELECT * FROM PARTITIONS WHERE table_schema='public' AND table_name='test_p'\G
 ```
 
+示例输出如下：
+
 ```sql
 *************************** 1. row ***************************
  table_catalog: greptime

docs/nightly/zh/user-guide/operations/admin.md

@@ -12,7 +12,24 @@
 ### 运行时信息
 
 * 通过 [CLUSTER_INFO](/reference/sql/information-schema/cluster-info.md) 表查找集群的拓扑信息。
-* 通过 [REGION_PEERS](/reference/sql/information-schema/region-peers.md) 表查找表的 Region 分布。
+* 通过 [PARTITIONS](reference/sql/information-schema/partitions.md) 表和[REGION_PEERS](/reference/sql/information-schema/region-peers.md) 表查找表的 Region 分布。
+
+例如查询一张表的所有 Region Id:
+
+```sql
+SELECT greptime_partition_id FROM PARTITIONS WHERE table_name = 'monitor'
+```
+
+查询一张表的 region 分布在哪些 datanode 上：
+
+```sql
+SELECT b.peer_id as datanode_id,
+ a.greptime_partition_id as region_id
+FROM information_schema.partitions a LEFT JOIN information_schema.region_peers b
+ON a.greptime_partition_id = b.region_id
+WHERE a.table_name='monitor'
+ORDER BY datanode_id ASC
+```
 
 `INFORMATION_SCHEMA` 数据库提供了对系统元数据的访问，如数据库或表的名称、列的数据类型等。请阅读 [参考文档](/reference/sql/information-schema/overview.md)。