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更新时间：2024-05-17 GMT+08:00
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分区表（母表）

实际对用户体现的表，用户对该表进行常规DML语句的增、删、查、改操作。通常使用在建表DDL语句显式的使用PARTITION BY语句进行定义，创建成功以后在pg_class表中新增一个entry，并且parttype列内容为'p'（一级分区）或者's'（二级分区），表明该entry为分区表的母表。分区母表通常是一个逻辑形态，对应的表文件并不存放数据。

示例1：t1_hash为一个一级分区表，分区类型为hash： 
gaussdb=# CREATE TABLE t1_hash (c1 INT, c2 INT, c3 INT)
PARTITION BY HASH(c1)
(
    PARTITION p0,
    PARTITION p1,
    PARTITION p2,
    PARTITION p3,
    PARTITION p4,
    PARTITION p5,
    PARTITION p6,
    PARTITION p7,
    PARTITION p8,
    PARTITION p9
);
gaussdb=# \d+ t1_hash
                      Table "public.t1_hash"
 Column |  Type   | Modifiers | Storage | Stats target | Description
--------+---------+-----------+---------+--------------+-------------
 c1     | integer |           | plain   |              |
 c2     | integer |           | plain   |              |
 c3     | integer |           | plain   |              |
Partition By HASH(c1)
Number of partitions: 10 (View pg_partition to check each partition range.)
Has OIDs: no
Options: orientation=row, compression=no, storage_type=USTORE, segment=off

--查询t1_hash分区类型
gaussdb=# SELECT relname, parttype FROM pg_class WHERE relname = 't1_hash';
 relname | parttype
---------+----------
 t1_hash | p           
(1 row)

--清理示例
gaussdb=# DROP TABLE t1_hash;
示例2：t1_sub_rr为一个二级分区表，分区类型为range-list： 
gaussdb=# CREATE TABLE t1_sub_rr (
    c1 INT,
    c2 INT,
    c3 INT
)
PARTITION BY RANGE (c1) 
SUBPARTITION BY LIST (c2) 
(
    PARTITION p_2021 VALUES LESS THAN (2022) (
        SUBPARTITION p_2021_1 VALUES (1),
        SUBPARTITION p_2021_2 VALUES (2),
        SUBPARTITION p_2021_3 VALUES (3)
    ),
    PARTITION p_2022 VALUES LESS THAN (2023) (
        SUBPARTITION p_2022_1 VALUES (1),
        SUBPARTITION p_2022_2 VALUES (2),
        SUBPARTITION p_2022_3 VALUES (3)
    ),
    PARTITION p_2023 VALUES LESS THAN (2024) (
        SUBPARTITION p_2023_1 VALUES (1),
        SUBPARTITION p_2023_2 VALUES (2),
        SUBPARTITION p_2023_3 VALUES (3)
    ),
    PARTITION p_2024 VALUES LESS THAN (2025) (
        SUBPARTITION p_2024_1 VALUES (1),
        SUBPARTITION p_2024_2 VALUES (2),
        SUBPARTITION p_2024_3 VALUES (3)
    ),
    PARTITION p_2025 VALUES LESS THAN (2026) (
        SUBPARTITION p_2025_1 VALUES (1),
        SUBPARTITION p_2025_2 VALUES (2),
        SUBPARTITION p_2025_3 VALUES (3)
    ),
    PARTITION p_2026 VALUES LESS THAN (2027) (
        SUBPARTITION p_2026_1 VALUES (1),
        SUBPARTITION p_2026_2 VALUES (2),
        SUBPARTITION p_2026_3 VALUES (3)
    )
);

gaussdb=# \d+ t1_sub_rr
                    Table "public.t1_sub_rr"
 Column |  Type   | Modifiers | Storage | Stats target | Description
--------+---------+-----------+---------+--------------+-------------
 c1     | integer |           | plain   |              |
 c2     | integer |           | plain   |              |
 c3     | integer |           | plain   |              |
Partition By RANGE(c1) Subpartition By LIST(c2)
Number of partitions: 6 (View pg_partition to check each partition range.)
Number of subpartitions: 18 (View pg_partition to check each subpartition range.)
Has OIDs: no
Options: orientation=row, compression=no, storage_type=USTORE, segment=off

--查询t1_sub_rr分区类型
gaussdb=# SELECT relname, parttype FROM pg_class WHERE relname = 't1_sub_rr';
  relname  | parttype
-----------+----------
 t1_sub_rr | s      
(1 row)

--清理示例
gaussdb=# DROP TABLE t1_sub_rr;
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