PARTITIONS
PARTITIONS 表提供了关于分区表的信息。
USE INFORMATION_SCHEMA;
DESC PARTITIONS;
结果如下：
+-------------------------------+----------+------+------+---------+---------------+
| Column | Type | Key | Null | Default | Semantic Type |
+-------------------------------+----------+------+------+---------+---------------+
| table_catalog | String | | NO | | FIELD |
| table_schema | String | | NO | | FIELD |
| table_name | String | | NO | | FIELD |
| partition_name | String | | NO | | FIELD |
| subpartition_name | String | | YES | | FIELD |
| partition_ordinal_position | Int64 | | YES | | FIELD |
| subpartition_ordinal_position | Int64 | | YES | | FIELD |
| partition_method | String | | YES | | FIELD |
| subpartition_method | String | | YES | | FIELD |
| partition_expression | String | | YES | | FIELD |
| subpartition_expression | String | | YES | | FIELD |
| partition_description | String | | YES | | FIELD |
| table_rows | Int64 | | YES | | FIELD |
| avg_row_length | Int64 | | YES | | FIELD |
| data_length | Int64 | | YES | | FIELD |
| max_data_length | Int64 | | YES | | FIELD |
| index_length | Int64 | | YES | | FIELD |
| data_free | Int64 | | YES | | FIELD |
| create_time | DateTime | | YES | | FIELD |
| update_time | DateTime | | YES | | FIELD |
| check_time | DateTime | | YES | | FIELD |
| checksum | Int64 | | YES | | FIELD |
| partition_comment | String | | YES | | FIELD |
| nodegroup | String | | YES | | FIELD |
| tablespace_name | String | | YES | | FIELD |
| greptime_partition_id | UInt64 | | YES | | FIELD |
+-------------------------------+----------+------+------+---------+---------------+
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：
CREATE TABLE public.test_p (
a INT PRIMARY KEY,
b STRING,
ts TIMESTAMP TIME INDEX,
)
PARTITION ON COLUMNS (a) (
a < 10,
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：
*************************** 1. row ***************************
table_catalog: greptime
table_schema: public
table_name: test_p
partition_name: p0
subpartition_name: NULL
partition_ordinal_position: 1
subpartition_ordinal_position: NULL
partition_method: RANGE
subpartition_method: NULL
partition_expression: (a) VALUES LESS THAN (PartitionExpr { lhs: Column("a"), op: Lt, rhs: Value(Int32(10)) })
subpartition_expression: NULL
partition_description: NULL
table_rows: NULL
avg_row_length: NULL
data_length: NULL
max_data_length: NULL
index_length: NULL
data_free: NULL
create_time: 2024-04-01 10:49:49.468000
update_time: NULL
check_time: NULL
checksum: NULL
partition_comment: NULL
nodegroup: NULL
tablespace_name: NULL
greptime_partition_id: 4453881085952
*************************** 2. row ***************************
table_catalog: greptime
table_schema: public
table_name: test_p
partition_name: p1
subpartition_name: NULL
partition_ordinal_position: 2
subpartition_ordinal_position: NULL
partition_method: RANGE
subpartition_method: NULL
partition_expression: (a) VALUES LESS THAN (PartitionExpr { lhs: Column("a"), op: GtEq, rhs: Value(Int32(20)) })
subpartition_expression: NULL
partition_description: NULL
table_rows: NULL
avg_row_length: NULL
data_length: NULL
max_data_length: NULL
index_length: NULL
data_free: NULL
create_time: 2024-04-01 10:49:49.468000
update_time: NULL
check_time: NULL
checksum: NULL
partition_comment: NULL
nodegroup: NULL
tablespace_name: NULL
greptime_partition_id: 4453881085954
*************************** 3. row ***************************
table_catalog: greptime
table_schema: public
table_name: test_p
partition_name: p2
subpartition_name: NULL
partition_ordinal_position: 3
subpartition_ordinal_position: NULL
partition_method: RANGE
subpartition_method: NULL
partition_expression: (a) VALUES LESS THAN (PartitionExpr { lhs: Expr(PartitionExpr { lhs: Column("a"), op: Gt, rhs: Value(Int32(10)) }), op: And, rhs: Expr(PartitionExpr { lhs: Column("a"), op: Lt, rhs: Value(Int32(20)) }) })
subpartition_expression: NULL
partition_description: NULL
table_rows: NULL
avg_row_length: NULL
data_length: NULL
max_data_length: NULL
index_length: NULL
data_free: NULL
create_time: 2024-04-01 10:49:49.468000
update_time: NULL
check_time: NULL
checksum: NULL
partition_comment: NULL
nodegroup: NULL
tablespace_name: NULL
greptime_partition_id: 4453881085953