分区（分区子表、子分区）

分区表中实际保存数据的表，对应的entry通常保存在pg_partition中，各个子分区的parentid作为外键关联其分区母表在pg_class表中的oid列。

示例1：t1_hash为一个一级分区表：

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
);

--查询t1_hash分区类型
gaussdb=# SELECT oid, relname, parttype FROM pg_class WHERE relname = 't1_hash';
  oid  | relname | parttype
-------+---------+----------
 16685 | t1_hash | p      
(1 row)

--查询t1_hash的分区信息
gaussdb=# SELECT oid, relname, parttype, parentid FROM pg_partition WHERE parentid = 16685;
  oid  | relname | parttype | parentid
-------+---------+----------+----------
 16688 | t1_hash | r        |    16685
 16689 | p0      | p        |    16685
 16690 | p1      | p        |    16685
 16691 | p2      | p        |    16685
 16692 | p3      | p        |    16685
 16693 | p4      | p        |    16685
 16694 | p5      | p        |    16685
 16695 | p6      | p        |    16685
 16696 | p7      | p        |    16685
 16697 | p8      | p        |    16685
 16698 | p9      | p        |    16685
(11 rows)