PostgreSQL12.5中分区表的一些操作实例
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1、创建一个有DEFAULT的分区表
1、先创建主表
create table tbl_log
(
id serial,
create_time timestamp(0) without time zone,
remark char(1)
) PARTITION BY RANGE (create_time);
#因为是serial类型，自增的所以会自动创建一个序列
postgres=# \d
List of relations
Schema | Name | Type | Owner
--------+----------------+-------------------+----------
public | tbl_log | partitioned table | postgres
public | tbl_log_id_seq | sequence | postgres
(7 rows)
2、如果没有创建分区就直接插入数据会报错
postgres=# INSERT INTO tbl_log(id, create_time, remark) VALUES (1, '2018-02-01', 'a');
ERROR: no partition of relation "tbl_log" found for row
DETAIL: Partition key of the failing row contains (create_time) = (2018-02-01 00:00:00).
postgres=#
3、创建分区
#包括左边1.1，不包括2.1
CREATE TABLE tbl_log_p201801 PARTITION OF tbl_log FOR VALUES FROM ('2018-01-01') TO ('2018-02-01');
CREATE TABLE tbl_log_p201802 PARTITION OF tbl_log FOR VALUES FROM ('2018-02-01') TO ('2018-03-01');
CREATE TABLE tbl_log_p201803 PARTITION OF tbl_log FOR VALUES FROM ('2018-03-01') TO ('2018-04-01');
CREATE TABLE tbl_log_default PARTITION OF tbl_log DEFAULT;
INSERT INTO tbl_log(id, create_time, remark) VALUES (1, '2018-02-01', 'a');
INSERT INTO tbl_log(id, create_time, remark) VALUES (2, '2018-03-01', 'b');
INSERT INTO tbl_log(id, create_time, remark) VALUES (3, '2018-04-01', 'd');
INSERT INTO tbl_log(id, create_time, remark) VALUES (4, '2020-07-01', 'c');
4、查看分区情况
postgres=# select * from tbl_log;
id | create_time | remark
----+---------------------+--------
1 | 2018-02-01 00:00:00 | a
2 | 2018-03-01 00:00:00 | b
3 | 2018-04-01 00:00:00 | d
4 | 2020-07-01 00:00:00 | c
(4 rows)
postgres=# select * from tbl_log_p201801;
id | create_time | remark
----+-------------+--------
(0 rows)
postgres=# select * from tbl_log_p201802;
id | create_time | remark
----+---------------------+--------
1 | 2018-02-01 00:00:00 | a
(1 row)
postgres=# select * from tbl_log_p201803;
id | create_time | remark
----+---------------------+--------
2 | 2018-03-01 00:00:00 | b
(1 row)
postgres=# select * from tbl_log_default;
id | create_time | remark
----+---------------------+--------
3 | 2018-04-01 00:00:00 | d
4 | 2020-07-01 00:00:00 | c
(2 rows)
postgres=#
2、有default 分区，再加分区
因为有default 分区，再加分区，所以会报错
postgres=# CREATE TABLE tbl_log_p201804 PARTITION OF tbl_log FOR VALUES FROM ('2018-04-01') TO ('2018-05-01');
ERROR: updated partition constraint for default partition "tbl_log_default" would be violated by some row
解决办法：
以上添加分区报错，需要解绑default分区，之后再添加，如下
1、解绑Default分区
postgres=# ALTER TABLE tbl_log DETACH PARTITION tbl_log_default;
ALTER TABLE
2、创建想要的分区
postgres=# CREATE TABLE tbl_log_p201804 PARTITION OF tbl_log FOR VALUES FROM ('2018-04-01') TO ('2018-05-01');
CREATE TABLE
3、分区创建成功，分区创建之后需把DEFAULT分区连接。
连接DEFAULT分区报错，如下:
postgres=# ALTER TABLE tbl_log ATTACH PARTITION tbl_log_default DEFAULT;
ERROR: partition constraint is violated by some row
postgres=# INSERT INTO tbl_log_p201804 SELECT * FROM tbl_log_default;
ERROR: new row for relation "tbl_log_p201804" violates partition constraint
DETAIL: Failing row contains (4, 2020-07-01 00:00:00, c).
因为tbl_log_default分区内有2018-04-01的数据，把这个数据从tbl_log_default中导出到对应的分区，并清理tbl_log_default中的对应的数据
postgres=# INSERT INTO tbl_log_p201804 SELECT * FROM tbl_log_default where create_time>='2018-04-01' and create_time<'2018-05-01';
INSERT 0 1
postgres=# delete from tbl_log_default where create_time>='2018-04-01' and create_time<'2018-05-01';
DELETE 1
4、再次连接DEFAULT分区成功
postgres=# ALTER TABLE tbl_log ATTACH PARTITION tbl_log_default DEFAULT;
ALTER TABLE
3、没有default的分区
创建没有default的分区，当插入的数据超过规划好的分区的时候会报错
1、创建1月份分区
create table tbl_log2
(
id serial,
create_time timestamp(0) without time zone,
remark char(1)
) PARTITION BY RANGE (create_time);
CREATE TABLE tbl_log2_p201801 PARTITION OF tbl_log2 FOR VALUES FROM ('2018-01-01') TO ('2018-02-01');
插入2月的数据就会报错
postgres=# INSERT INTO tbl_log2(id, create_time, remark) VALUES (1, '2018-01-01', 'a');
INSERT 0 1
postgres=# INSERT INTO tbl_log2(id, create_time, remark) VALUES (1, '2018-02-01', 'a');
ERROR: no partition of relation "tbl_log2" found for row
DETAIL: Partition key of the failing row contains (create_time) = (2018-02-01 00:00:00).
4、给分区表ddl
4.1、在原来没有主键的分区表加主键
结论：
1、在主表加主键，主键为仅仅想要的主键，会报错，需要用想要的主键+分区键组合为主键
2、分区表可以单独添加主键
1.1、在主表加主键，主键为仅仅想要的主键，报错如下 must include all partitioning columns
postgres=# alter table tbl_log add primary key(id);
ERROR: unique constraint on partitioned table must include all partitioning columns
DETAIL: PRIMARY KEY constraint on table "tbl_log" lacks column "create_time" which is part of the partition key.
postgres=# alter table tbl_log add primary key(id)
1.2、在主表添加主键需要是想要的主键+分区键
postgres=# alter table tbl_log add primary key (id,create_time);
ALTER TABLE
postgres=# \d tbl_log
Partitioned table "public.tbl_log"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | not null |
remark | character(1) | | |
name | character varying(2) | | |
Partition key: RANGE (create_time)
Indexes:
"tbl_log_pkey" PRIMARY KEY, btree (id, create_time)
Number of partitions: 5 (Use \d+ to list them.)
postgres=# \d tbl_log_p201801
Table "public.tbl_log_p201801"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | not null |
remark | character(1) | | |
name | character varying(2) | | |
Partition of: tbl_log FOR VALUES FROM ('2018-01-01 00:00:00') TO ('2018-02-01 00:00:00')
Indexes:
"tbl_log_p201801_pkey" PRIMARY KEY, btree (id, create_time)
1.3、可以给分区表单独添加主键
postgres=# alter table tbl_log_p201801 add primary key (id);
ALTER TABLE
postgres=# \d tbl_log_p201801
Table "public.tbl_log_p201801"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | |
remark | character(1) | | |
name | character varying(2) | | |
Partition of: tbl_log FOR VALUES FROM ('2018-01-01 00:00:00') TO ('2018-02-01 00:00:00')
Indexes:
"tbl_log_p201801_pkey" PRIMARY KEY, btree (id)
postgres=#
4.2、创建分区表时，就指定主键
主键不包括分区键，报错提示must include all partitioning columns
create table tbl_log2
(
id int,
create_time timestamp(0) without time zone,
remark char(1),
primary key (id)
);
ERROR: unique constraint on partitioned table must include all partitioning columns
DETAIL: PRIMARY KEY constraint on table "tbl_log2" lacks column "create_time" which is part of the partition key.
修改语句，添加分区键也为主键，创建成功
create table tbl_log2
(
id int,
create_time timestamp(0) without time zone,
remark char(1),
primary key (id,create_time)
) PARTITION BY RANGE (create_time);
CREATE TABLE
4.3、分区表加字段，修改字段
1、加字段，可以成功添加，在主表加字段，分区表会自动添加
postgres=# alter table tbl_log add name varchar(2);
ALTER TABLE
postgres=# \d tbl_log;
Partitioned table "public.tbl_log"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | |
remark | character(1) | | |
name | character varying(2) | | |
Partition key: RANGE (create_time)
Number of partitions: 5 (Use \d+ to list them.)
postgres=# \d tbl_log_p201801;
Table "public.tbl_log_p201801"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | |
remark | character(1) | | |
name | character varying(2) | | |
Partition of: tbl_log FOR VALUES FROM ('2018-01-01 00:00:00') TO ('2018-02-01 00:00:00')
2、直接在分区表加字段会报错
postgres=# alter table tbl_log_p201801 add name2 varchar(2);
ERROR: cannot add column to a partition
3、修改字段
postgres=# alter table tbl_log alter column remark type varchar(10);
ALTER TABLE
postgres=# \d tbl_log;
Partitioned table "public.tbl_log"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | not null |
remark | character varying(10) | | |
name | character varying(2) | | |
Partition key: RANGE (create_time)
Indexes:
"tbl_log_pkey" PRIMARY KEY, btree (id, create_time)
Number of partitions: 5 (Use \d+ to list them.)
postgres=# \d tbl_log_p201801
Table "public.tbl_log_p201801"
Column | Type | Collation | Nullable | Default
-------------+--------------------------------+-----------+----------+-------------------------------------
id | integer | | not null | nextval('tbl_log_id_seq'::regclass)
create_time | timestamp(0) without time zone | | not null |
remark | character varying(10) | | |
name | character varying(2) | | |
Partition of: tbl_log FOR VALUES FROM ('2018-01-01 00:00:00') TO ('2018-02-01 00:00:00')
Indexes:
"tbl_log_p201801_pkey" PRIMARY KEY, btree (id, create_time)
postgres=#
总结
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