PostgreSQL11:分区表支持创建主键、外键、索引

PostgreSQL 10 版本虽然支持创建范围分区表和列表分区表,但创建过程依然比较繁琐,需要手工定义子表索引、主键,详见 PostgreSQL10:重量级新特性-支持分区表,PostgreSQL 11 版本得到增强,在父表上创建索引、主键、外键后,子表上将自动创建,本文演示这三种场景。

值得一提的是,11 版本之前 PostgreSQL 的分区表不支持全局主键,虽然可以在父表和子表上分别定义主键,但不支持全局主键,也就是说,父表和子表、子表和子表的主键数据可以重复。

手册上的 Release 说明

Support for PRIMARY KEY, FOREIGN KEY, indexes, and triggers on partitioned tables

本文以创建哈希分区表为例进行测试。

测试环境准备

创建分区表并插入测试数据,为后续测试做准备。

创建父表

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CREATE TABLE userinfo (
userid int4,
username character varying(64),
ctime timestamp(6) without time zone
) PARTITION BY HASH(userid);

创建子表

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CREATE TABLE userinfo_p0 PARTITION OF userinfo FOR VALUES WITH(MODULUS 4, REMAINDER 0);
CREATE TABLE userinfo_p1 PARTITION OF userinfo FOR VALUES WITH(MODULUS 4, REMAINDER 1);
CREATE TABLE userinfo_p2 PARTITION OF userinfo FOR VALUES WITH(MODULUS 4, REMAINDER 2);
CREATE TABLE userinfo_p3 PARTITION OF userinfo FOR VALUES WITH(MODULUS 4, REMAINDER 3);

插入数据

给分区表插入100万数据,如下:

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INSERT INTO userinfo(userid,username,ctime) SELECT n, n || '_username',clock_timestamp() FROM generate_series(1,1000000) n;

测试一: 创建主键

在父表上创建主键,如下。

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ALTER TABLE userinfo ADD PRIMARY KEY (userid);

在父表上查看,如下。

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francs=> \d userinfo
Table "francs.userinfo"
Column | Type | Collation | Nullable | Default
----------+--------------------------------+-----------+----------+---------
userid | integer | | not null |
username | character varying(64) | | |
ctime | timestamp(6) without time zone | | |
Partition key: HASH (userid)
Indexes:
"userinfo_pkey" PRIMARY KEY, btree (userid)
Number of partitions: 4 (Use \d+ to list them.)

查看子表,发现子表上也有了主键。

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francs=> \d userinfo_p0
Table "francs.userinfo_p0"
Column | Type | Collation | Nullable | Default
----------+--------------------------------+-----------+----------+---------
userid | integer | | not null |
username | character varying(64) | | |
ctime | timestamp(6) without time zone | | |
Partition of: userinfo FOR VALUES WITH (modulus 4, remainder 0)
Indexes:
"userinfo_p0_pkey" PRIMARY KEY, btree (userid)

此主键为全局主键,子表间的主键之间不能有重复数据。

测试二: 创建索引

在父表上创建索引,如下

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francs=> CREATE INDEX idx_userinfo_username ON userinfo USING BTREE(username);
CREATE INDEX

发现父表和子表上都创建了索引,如下。

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francs=> \d userinfo
Table "francs.userinfo"
Column | Type | Collation | Nullable | Default
----------+--------------------------------+-----------+----------+---------
userid | integer | | not null |
username | character varying(64) | | |
ctime | timestamp(6) without time zone | | |
Partition key: HASH (userid)
Indexes:
"userinfo_pkey" PRIMARY KEY, btree (userid)
"idx_userinfo_username" btree (username)
Number of partitions: 4 (Use \d+ to list them.)

francs=> \d userinfo_p1
Table "francs.userinfo_p1"
Column | Type | Collation | Nullable | Default
----------+--------------------------------+-----------+----------+---------
userid | integer | | not null |
username | character varying(64) | | |
ctime | timestamp(6) without time zone | | |
Partition of: userinfo FOR VALUES WITH (modulus 4, remainder 1)
Indexes:
"userinfo_p1_pkey" PRIMARY KEY, btree (userid)
"userinfo_p1_username_idx" btree (username)

测试三: 创建外键

例如两张表,supplier_groups 和 supplier 分别用来存储供应商分组和供应商信, 如下。

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CREATE TABLE supplier_groups(
group_id int4 PRIMARY KEY,
group_name text
);

CREATE TABLE suppliers (
supplier_id int4 PRIMARY KEY,
supplier_name text,
group_id int4 REFERENCES supplier_groups(group_id)
) PARTITION BY HASH (supplier_id);

创建子表

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CREATE TABLE suppliers_p0 PARTITION OF suppliers FOR VALUES WITH(MODULUS 4, REMAINDER 0);
CREATE TABLE suppliers_p1 PARTITION OF suppliers FOR VALUES WITH(MODULUS 4, REMAINDER 1);
CREATE TABLE suppliers_p2 PARTITION OF suppliers FOR VALUES WITH(MODULUS 4, REMAINDER 2);
CREATE TABLE suppliers_p3 PARTITION OF suppliers FOR VALUES WITH(MODULUS 4, REMAINDER 3);

查看子表

查看子表,发现子表上也自动创建了外键。

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francs=> \d suppliers_p0
Table "francs.suppliers_p0"
Column | Type | Collation | Nullable | Default
---------------+---------+-----------+----------+---------
supplier_id | integer | | not null |
supplier_name | text | | |
group_id | integer | | |
Partition of: suppliers FOR VALUES WITH (modulus 4, remainder 0)
Indexes:
"suppliers_p0_pkey" PRIMARY KEY, btree (supplier_id)
Foreign-key constraints:
"suppliers_group_id_fkey" FOREIGN KEY (group_id) REFERENCES supplier_groups(group_id)

总结

以上演示了 PostgreSQL 11 分区表在父表上创建索引、主键、外键后,子表会自动创建相应索引、主键、外键,相比10版本极大减少了分区表维护工作量。

参考

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