Partitioned Table

Updated on 2024-05-20 GMT+08:00

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A table that is displayed to users. Users can add, delete, query, and modify data in the table using common DML statements. Generally, it is defined by explicitly using the PARTITION BY statement when DDL statements are used for creating a table. After the table is created, an entry is added to the pg_class table, and the content in the parttype column is 'p' (level-1 partition) or 's' (level-2 partition), indicating that the entry is a partitioned table. The partitioned table is usually a logical form, and does not store any data.

Example 1: t1_hash is a partitioned table whose partitioning type is 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

-- Query the partitioning type of table t1_hash.
gaussdb=# SELECT relname, parttype FROM pg_class WHERE relname = 't1_hash';
 relname | parttype
---------+----------
 t1_hash | p           
(1 row)

-- Cleanup example
gaussdb=# DROP TABLE t1_hash;

Example 2: t1_sub_rr is a level-2 partitioned table whose partitioning type is 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

-- Query the partitioning type of table t1_sub_rr.
gaussdb=# SELECT relname, parttype FROM pg_class WHERE relname = 't1_sub_rr';
  relname  | parttype
-----------+----------
 t1_sub_rr | s      
(1 row)

-- Cleanup example
gaussdb=# DROP TABLE t1_sub_rr;

Parent topic: Basic Concepts

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