PostgreSQL分区表实现——pg_pathman分区表管理
该博文用于自己学习记录，内容节选自： https://github.com/digoal/blog/blob/master/201610/20161024_01.md
pg_pathman 创建分区表时，需要指定主表的名字，主表必须已存在，主表可以有数据，也可以是空表。
如果主表有数据，那么可以配置是否需要在创建分区时，将数据迁移到分区，（不建议对大表这么做）。
如果主表有很多数据，建议使用后台非堵塞式的迁移方法。 （调用partition_table_concurrently()函数进行迁移）。
如果在创建分区表前，使用set_init_callback(relation regclass, callback regproc DEFAULT 0)设置了回调函数，则创建分区时，每个分区表创建是，会自动调用对应的回调函数。
回调函数的传入参数和模式如下
$part_init_callback$(args JSONB) RETURNS VOID
传入参数如下
/* RANGE-partitioned table abc (for exp: child abc_4) */
{
"parent": "abc",
"parttype": "2",
"partition": "abc_4",
"range_max": "401",
"range_min": "301"
}
/* HASH-partitioned table abc (for exp: child abc_0) */
{
"parent": "abc",
"parttype": "1",
"partition": "abc_0"
}
1. range分区
有4个管理函数用来创建范围分区
指定起始值、间隔、分区个数
create_range_partitions(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分区列名
start_value ANYELEMENT, -- 开始值
p_interval ANYELEMENT, -- 间隔；任意类型，适合任意类型的分区表
p_count INTEGER DEFAULT NULL, -- 分多少个区
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即将数据从主表迁移到分区, 不建议这么使用, 建议使用非堵塞式的迁移( 调用partition_table_concurrently() )
create_range_partitions(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分区列名
start_value ANYELEMENT, -- 开始值
p_interval INTERVAL, -- 间隔；interval 类型，用于时间分区表
p_count INTEGER DEFAULT NULL, -- 分多少个区
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即将数据从主表迁移到分区, 不建议这么使用, 建议使用非堵塞式的迁移( 调用partition_table_concurrently() )
指定起始值、终值、间隔
create_partitions_from_range(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分区列名
start_value ANYELEMENT, -- 开始值
end_value ANYELEMENT, -- 结束值
p_interval ANYELEMENT, -- 间隔；任意类型，适合任意类型的分区表
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即将数据从主表迁移到分区, 不建议这么使用, 建议使用非堵塞式的迁移( 调用partition_table_concurrently() )
create_partitions_from_range(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分区列名
start_value ANYELEMENT, -- 开始值
end_value ANYELEMENT, -- 结束值
p_interval INTERVAL, -- 间隔；interval 类型，用于时间分区表
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即将数据从主表迁移到分区, 不建议这么使用, 建议使用非堵塞式的迁移( 调用partition_table_concurrently() )
例子
创建需要分区的主表
postgres=# create table part_test(id int, info text, crt_time timestamp not null); -- 分区列必须有not null约束
CREATE TABLE
插入一批测试数据，模拟已经有数据了的主表
postgres=# insert into part_test select id,md5(random()::text),clock_timestamp() + (id||' hour')::interval from generate_series(1,10000) t(id);
INSERT 0 10000
postgres=# select * from part_test limit 10;
id | info | crt_time
----+----------------------------------+----------------------------
1 | 36fe1adedaa5b848caec4941f87d443a | 2016-10-25 10:27:13.206713
2 | c7d7358e196a9180efb4d0a10269c889 | 2016-10-25 11:27:13.206893
3 | 005bdb063550579333264b895df5b75e | 2016-10-25 12:27:13.206904
4 | 6c900a0fc50c6e4da1ae95447c89dd55 | 2016-10-25 13:27:13.20691
5 | 857214d8999348ed3cb0469b520dc8e5 | 2016-10-25 14:27:13.206916
6 | 4495875013e96e625afbf2698124ef5b | 2016-10-25 15:27:13.206921
7 | 82488cf7e44f87d9b879c70a9ed407d4 | 2016-10-25 16:27:13.20693
8 | a0b92547c8f17f79814dfbb12b8694a0 | 2016-10-25 17:27:13.206936
9 | 2ca09e0b85042b476fc235e75326b41b | 2016-10-25 18:27:13.206942
10 | 7eb762e1ef7dca65faf413f236dff93d | 2016-10-25 19:27:13.206947
(10 rows)
注意:
1. 分区列必须有not null约束
2. 分区个数必须能覆盖已有的所有记录
创建分区，每个分区包含1个月的跨度数据
postgres=# select
create_range_partitions('part_test'::regclass, -- 主表OID
'crt_time', -- 分区列名
'2016-10-25 00:00:00'::timestamp, -- 开始值
interval '1 month', -- 间隔；interval 类型，用于时间分区表
24, -- 分多少个区
false) ; -- 不迁移数据
NOTICE: sequence "part_test_seq" does not exist, skipping
create_range_partitions
-------------------------
24
(1 row)
postgres-# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_1,
part_test_10,
part_test_11,
part_test_12,
part_test_13,
part_test_14,
part_test_15,
part_test_16,
part_test_17,
part_test_18,
part_test_19,
part_test_2,
part_test_20,
part_test_21,
part_test_22,
part_test_23,
part_test_24,
part_test_3,
part_test_4,
part_test_5,
part_test_6,
part_test_7,
part_test_8,
part_test_9
由于不迁移数据，所以数据还在主表
postgres=# select count(*) from only part_test;
count
-------
10000
(1 row)
使用非堵塞式的迁移接口
partition_table_concurrently(relation REGCLASS, -- 主表OID
batch_size INTEGER DEFAULT 1000, -- 一个事务批量迁移多少记录
sleep_time FLOAT8 DEFAULT 1.0) -- 获得行锁失败时，休眠多久再次获取，重试60次退出任务。
postgres=# select partition_table_concurrently('part_test'::regclass,
10000,
1.0);
NOTICE: worker started, you can stop it with the following command: select stop_concurrent_part_task('part_test');
partition_table_concurrently
------------------------------
(1 row)
迁移结束后，主表数据已经没有了，全部在分区中
postgres=# select count(*) from only part_test;
count
-------
0
(1 row)
数据迁移完成后，建议禁用主表，这样执行计划就不会出现主表了
postgres=# select set_enable_parent('part_test'::regclass, false);
set_enable_parent
-------------------
(1 row)
postgres=# explain select * from part_test where crt_time = '2016-10-25 00:00:00'::timestamp;
QUERY PLAN
---------------------------------------------------------------------------------
Append (cost=0.00..16.18 rows=1 width=45)
-> Seq Scan on part_test_1 (cost=0.00..16.18 rows=1 width=45)
Filter: (crt_time = '2016-10-25 00:00:00'::timestamp without time zone)
(3 rows)
建议
1. 分区列必须有not null约束
2. 分区个数必须能覆盖已有的所有记录
3. 建议使用非堵塞式迁移接口
4. 建议数据迁移完成后，禁用主表
2. hash分区
有1个管理函数用来创建范围分区
指定起始值、间隔、分区个数
create_hash_partitions(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分区列名
partitions_count INTEGER, -- 打算创建多少个分区
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即将数据从主表迁移到分区, 不建议这么使用, 建议使用非堵塞式的迁移( 调用partition_table_concurrently() )
例子
创建需要分区的主表
postgres=# create table part_test(id int, info text, crt_time timestamp not null); -- 分区列必须有not null约束
CREATE TABLE
插入一批测试数据，模拟已经有数据了的主表
postgres=# insert into part_test select id,md5(random()::text),clock_timestamp() + (id||' hour')::interval from generate_series(1,10000) t(id);
INSERT 0 10000
postgres=# select * from part_test limit 10;
id | info | crt_time
----+----------------------------------+----------------------------
1 | 29ce4edc70dbfbe78912beb7c4cc95c2 | 2016-10-25 10:47:32.873879
2 | e0990a6fb5826409667c9eb150fef386 | 2016-10-25 11:47:32.874048
3 | d25f577a01013925c203910e34470695 | 2016-10-25 12:47:32.874059
4 | 501419c3f7c218e562b324a1bebfe0ad | 2016-10-25 13:47:32.874065
5 | 5e5e22bdf110d66a5224a657955ba158 | 2016-10-25 14:47:32.87407
6 | 55d2d4fd5229a6595e0dd56e13d32be4 | 2016-10-25 15:47:32.874076
7 | 1dfb9a783af55b123c7a888afe1eb950 | 2016-10-25 16:47:32.874081
8 | 41eeb0bf395a4ab1e08691125ae74bff | 2016-10-25 17:47:32.874087
9 | 83783d69cc4f9bb41a3978fe9e13d7fa | 2016-10-25 18:47:32.874092
10 | affc9406d5b3412ae31f7d7283cda0dd | 2016-10-25 19:47:32.874097
(10 rows)
注意:
1. 分区列必须有not null约束
创建128个分区
postgres=# select
create_hash_partitions('part_test'::regclass, -- 主表OID
'crt_time', -- 分区列名
128, -- 打算创建多少个分区
false) ; -- 不迁移数据
create_hash_partitions
------------------------
128
(1 row)
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_0,
part_test_1,
part_test_10,
part_test_100,
part_test_101,
part_test_102,
part_test_103,
part_test_104,
part_test_105,
part_test_106,
part_test_107,
part_test_108,
part_test_109,
part_test_11,
part_test_110,
part_test_111,
part_test_112,
part_test_113,
part_test_114,
part_test_115,
part_test_116,
part_test_117,
part_test_118,
part_test_119,
part_test_12,
part_test_120,
part_test_121,
part_test_122,
part_test_123,
part_test_124,
part_test_125,
part_test_126,
part_test_127,
part_test_13,
part_test_14,
part_test_15,
part_test_16,
part_test_17,
part_test_18,
part_test_19,
part_test_2,
part_test_20,
part_test_21,
part_test_22,
part_test_23,
part_test_24,
part_test_25,
part_test_26,
part_test_27,
part_test_28,
part_test_29,
part_test_3,
part_test_30,
part_test_31,
part_test_32,
part_test_33,
part_test_34,
part_test_35,
part_test_36,
part_test_37,
part_test_38,
part_test_39,
part_test_4,
part_test_40,
part_test_41,
part_test_42,
part_test_43,
part_test_44,
part_test_45,
part_test_46,
part_test_47,
part_test_48,
part_test_49,
part_test_5,
part_test_50,
part_test_51,
part_test_52,
part_test_53,
part_test_54,
part_test_55,
part_test_56,
part_test_57,
part_test_58,
part_test_59,
part_test_6,
part_test_60,
part_test_61,
part_test_62,
part_test_63,
part_test_64,
part_test_65,
part_test_66,
part_test_67,
part_test_68,
part_test_69,
part_test_7,
part_test_70,
part_test_71,
part_test_72,
part_test_73,
part_test_74,
part_test_75,
part_test_76,
part_test_77,
part_test_78,
part_test_79,
part_test_8,
part_test_80,
part_test_81,
part_test_82,
part_test_83,
part_test_84,
part_test_85,
part_test_86,
part_test_87,
part_test_88,
part_test_89,
part_test_9,
part_test_90,
part_test_91,
part_test_92,
part_test_93,
part_test_94,
part_test_95,
part_test_96,
part_test_97,
part_test_98,
part_test_99
由于不迁移数据，所以数据还在主表
postgres=# select count(*) from only part_test;
count
-------
10000
(1 row)
使用非堵塞式的迁移接口
partition_table_concurrently(relation REGCLASS, -- 主表OID
batch_size INTEGER DEFAULT 1000, -- 一个事务批量迁移多少记录
sleep_time FLOAT8 DEFAULT 1.0) -- 获得行锁失败时，休眠多久再次获取，重试60次退出任务。
postgres=# select partition_table_concurrently('part_test'::regclass,
10000,
1.0);
NOTICE: worker started, you can stop it with the following command: select stop_concurrent_part_task('part_test');
partition_table_concurrently
------------------------------
(1 row)
迁移结束后，主表数据已经没有了，全部在分区中
postgres=# select count(*) from only part_test;
count
-------
0
(1 row)
数据迁移完成后，建议禁用主表，这样执行计划就不会出现主表了
postgres=# select set_enable_parent('part_test'::regclass, false);
set_enable_parent
-------------------
(1 row)
只查单个分区
postgres=# explain select * from part_test where crt_time = '2016-10-25 00:00:00'::timestamp;
QUERY PLAN
---------------------------------------------------------------------------------
Append (cost=0.00..1.91 rows=1 width=45)
-> Seq Scan on part_test_122 (cost=0.00..1.91 rows=1 width=45)
Filter: (crt_time = '2016-10-25 00:00:00'::timestamp without time zone)
(3 rows)
分区表约束如下
很显然pg_pathman自动完成了转换，如果是传统的继承，select * from part_test where crt_time = '2016-10-25 00:00:00'::timestamp; 这种写法是不能筛选分区的。
postgres=# \d+ part_test_122
Table "public.part_test_122"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_122_3_check" CHECK (get_hash_part_idx(timestamp_hash(crt_time), 128) = 122)
Inherits: part_test
建议
1. 分区列必须有not null约束
2. 建议使用非堵塞式迁移接口
3. 建议数据迁移完成后，禁用主表
4. pg_pathman不会受制于表达式的写法，所以select * from part_test where crt_time = '2016-10-25 00:00:00'::timestamp;这样的写法也是能走哈希分区的。
5. hash分区列不局限于int类型的列，会使用hash函数自动转换。
3. 数据迁移到分区
如果创建分区表时，未将主表数据迁移到分区，那么可以使用非堵塞式的迁移接口，将数据迁移到分区
可能类似如下做法
with tmp as (delete from 主表 limit xx nowait returning *) insert into 分区 select * from tmp
或者使用 select array_agg(ctid) from 主表 limit xx for update nowati 进行标示 然后执行delete和insert。
1. 函数接口如下
partition_table_concurrently(relation REGCLASS, -- 主表OID
batch_size INTEGER DEFAULT 1000, -- 一个事务批量迁移多少记录
sleep_time FLOAT8 DEFAULT 1.0) -- 获得行锁失败时，休眠多久再次获取，重试60次退出任务。
2. 例子
postgres=# select partition_table_concurrently('part_test'::regclass,
10000,
1.0);
NOTICE: worker started, you can stop it with the following command: select stop_concurrent_part_task('part_test');
partition_table_concurrently
------------------------------
(1 row)
3. 如何停止迁移任务，调用如下函数接口
stop_concurrent_part_task(relation REGCLASS)
4. 查看后台的数据迁移任务
postgres=# select * from pathman_concurrent_part_tasks;
userid | pid | dbid | relid | processed | status
--------+-----+------+-------+-----------+--------
(0 rows)
4. 分裂范围分区
例如某个分区太大了，想分裂为两个分区，可以使用这种方法
仅支持范围分区表
split_range_partition(partition REGCLASS, -- 分区oid
split_value ANYELEMENT, -- 分裂值
partition_name TEXT DEFAULT NULL) -- 分裂后新增的分区表名
例子
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_1,
part_test_10,
part_test_11,
part_test_12,
part_test_13,
part_test_14,
part_test_15,
part_test_16,
part_test_17,
part_test_18,
part_test_19,
part_test_2,
part_test_20,
part_test_21,
part_test_22,
part_test_23,
part_test_24,
part_test_3,
part_test_4,
part_test_5,
part_test_6,
part_test_7,
part_test_8,
part_test_9
postgres=# \d+ part_test_1
Table "public.part_test_1"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_1_3_check" CHECK (crt_time >= '2016-10-25 00:00:00'::timestamp without time zone AND crt_time < '2016-11-25 00:00:00'::timestamp without time zone)
Inherits: part_test
分裂
postgres=# select split_range_partition('part_test_1'::regclass, -- 分区oid
'2016-11-10 00:00:00'::timestamp, -- 分裂值
'part_test_1_2'); -- 分区表名
split_range_partition
-----------------------------------------------
{"2016-10-25 00:00:00","2016-11-25 00:00:00"}
(1 row)
分裂后的两个表如下
postgres=# \d+ part_test_1
Table "public.part_test_1"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_1_3_check" CHECK (crt_time >= '2016-10-25 00:00:00'::timestamp without time zone AND crt_time < '2016-11-10 00:00:00'::timestamp without time zone)
Inherits: part_test
postgres=# \d+ part_test_1_2
Table "public.part_test_1_2"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_1_2_3_check" CHECK (crt_time >= '2016-11-10 00:00:00'::timestamp without time zone AND crt_time < '2016-11-25 00:00:00'::timestamp without time zone)
Inherits: part_test
数据会自动迁移到另一个分区
postgres=# select count(*) from part_test_1;
count
-------
373
(1 row)
postgres=# select count(*) from part_test_1_2;
count
-------
360
(1 row)
继承关系如下
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_1,
part_test_10,
part_test_11,
part_test_12,
part_test_13,
part_test_14,
part_test_15,
part_test_16,
part_test_17,
part_test_18,
part_test_19,
part_test_1_2, -- 新增的表
part_test_2,
part_test_20,
part_test_21,
part_test_22,
part_test_23,
part_test_24,
part_test_3,
part_test_4,
part_test_5,
part_test_6,
part_test_7,
part_test_8,
part_test_9
5. 合并范围分区
目前仅支持范围分区
调用如下接口
指定两个需要合并分区，必须为相邻分区
merge_range_partitions(partition1 REGCLASS, partition2 REGCLASS)
例子
postgres=# select merge_range_partitions('part_test_2'::regclass, 'part_test_12'::regclass) ;
ERROR: merge failed, partitions must be adjacent
CONTEXT: PL/pgSQL function merge_range_partitions_internal(regclass,regclass,regclass,anyelement) line 27 at RAISE
SQL statement "SELECT public.merge_range_partitions_internal($1, $2, $3, NULL::timestamp without time zone)"
PL/pgSQL function merge_range_partitions(regclass,regclass) line 44 at EXECUTE
不是相邻分区，报错
相邻分区可以合并
postgres=# select merge_range_partitions('part_test_1'::regclass, 'part_test_1_2'::regclass) ;
merge_range_partitions
------------------------
(1 row)
合并后，会删掉其中一个分区表
postgres=# \d part_test_1_2
Did not find any relation named "part_test_1_2".
postgres=# \d part_test_1
Table "public.part_test_1"
Column | Type | Modifiers
----------+-----------------------------+-----------
id | integer |
info | text |
crt_time | timestamp without time zone | not null
Check constraints:
"pathman_part_test_1_3_check" CHECK (crt_time >= '2016-10-25 00:00:00'::timestamp without time zone AND crt_time < '2016-11-25 00:00:00'::timestamp without time zone)
Inherits: part_test
postgres=# select count(*) from part_test_1;
count
-------
733
(1 row)
6. 向后添加范围分区
如果已经对主表进行了分区，将来需要增加分区的话，有几种方法，一种是向后新增分区（即在末尾追加分区）。
新增分区时，会使用初次创建该分区表时的interval作为间隔。
可以在这个表中查询每个分区表初次创建时的 interval
postgres=# select * from pathman_config;
partrel | attname | parttype | range_interval
-----------+----------+----------+----------------
part_test | crt_time | 2 | 1 mon
(1 row)
添加分区接口，支持指定表空间
append_range_partition(parent REGCLASS, -- 主表OID
partition_name TEXT DEFAULT NULL, -- 新增的分区表名, 默认不需要输入
tablespace TEXT DEFAULT NULL) -- 新增的分区表放到哪个表空间, 默认不需要输入
例子
postgres=# select append_range_partition('part_test'::regclass);
append_range_partition
------------------------
public.part_test_25
(1 row)
postgres=# \d+ part_test_25
Table "public.part_test_25"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_25_3_check" CHECK (crt_time >= '2018-10-25 00:00:00'::timestamp without time zone AND crt_time < '2018-11-25 00:00:00'::timestamp without time zone)
Inherits: part_test
postgres=# \d+ part_test_24
Table "public.part_test_24"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_24_3_check" CHECK (crt_time >= '2018-09-25 00:00:00'::timestamp without time zone AND crt_time < '2018-10-25 00:00:00'::timestamp without time zone)
Inherits: part_test
7. 向前添加范围分区
在头部追加分区。
接口
prepend_range_partition(parent REGCLASS,
partition_name TEXT DEFAULT NULL,
tablespace TEXT DEFAULT NULL)
例子
postgres=# select prepend_range_partition('part_test'::regclass);
prepend_range_partition
-------------------------
public.part_test_26
(1 row)
postgres=# \d+ part_test_26
Table "public.part_test_26"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_26_3_check" CHECK (crt_time >= '2016-09-25 00:00:00'::timestamp without time zone AND crt_time < '2016-10-25 00:00:00'::timestamp without time zone)
Inherits: part_test
postgres=# \d+ part_test_1
Table "public.part_test_1"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_1_3_check" CHECK (crt_time >= '2016-10-25 00:00:00'::timestamp without time zone AND crt_time < '2016-11-25 00:00:00'::timestamp without time zone)
Inherits: part_test
8. 添加分区
指定分区起始值的方式添加分区，只要创建的分区和已有分区不会存在数据交叉就可以创建成功。
也就是说使用这种方法，不要求强制创建连续的分区，例如已有分区覆盖了2010-2015的范围，你可以直接创建一个2020年的分区表，不需要覆盖2015到2020的范围。
接口如下
add_range_partition(relation REGCLASS, -- 主表OID
start_value ANYELEMENT, -- 起始值
end_value ANYELEMENT, -- 结束值
partition_name TEXT DEFAULT NULL, -- 分区名
tablespace TEXT DEFAULT NULL) -- 分区创建在哪个表空间下
例子
postgres=# select add_range_partition('part_test'::regclass, -- 主表OID
'2020-01-01 00:00:00'::timestamp, -- 起始值
'2020-02-01 00:00:00'::timestamp); -- 结束值
add_range_partition
---------------------
public.part_test_27
(1 row)
postgres=# \d+ part_test_27
Table "public.part_test_27"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_27_3_check" CHECK (crt_time >= '2020-01-01 00:00:00'::timestamp without time zone AND crt_time < '2020-02-01 00:00:00'::timestamp without time zone)
Inherits: part_test
9. 删除分区
1. 删除单个范围分区
接口如下
drop_range_partition(partition TEXT, -- 分区名称
delete_data BOOLEAN DEFAULT TRUE) -- 是否删除分区数据，如果false，表示分区数据迁移到主表。
Drop RANGE partition and all of its data if delete_data is true.
例子
删除分区， 数据迁移到主表
postgres=# select drop_range_partition('part_test_1',false);
NOTICE: 733 rows copied from part_test_1
drop_range_partition
----------------------
part_test_1
(1 row)
postgres=# select drop_range_partition('part_test_2',false);
NOTICE: 720 rows copied from part_test_2
drop_range_partition
----------------------
part_test_2
(1 row)
postgres=# select count(*) from part_test;
count
-------
10000
(1 row)
删除分区，分区数据也删除，不迁移到主表
postgres=# select drop_range_partition('part_test_3',true);
drop_range_partition
----------------------
part_test_3
(1 row)
postgres=# select count(*) from part_test;
count
-------
9256
(1 row)
postgres=# select count(*) from only part_test;
count
-------
1453
(1 row)
2. 删除所有分区，并且指定是否要将数据迁移到主表
接口如下
drop_partitions(parent REGCLASS,
delete_data BOOLEAN DEFAULT FALSE)
Drop partitions of the parent table (both foreign and local relations).
If delete_data is false, the data is copied to the parent table first.
Default is false.
例子
postgres=# select drop_partitions('part_test'::regclass, false); -- 删除所有分区表，并将数据迁移到主表
NOTICE: function public.part_test_upd_trig_func() does not exist, skipping
NOTICE: 744 rows copied from part_test_4
NOTICE: 672 rows copied from part_test_5
NOTICE: 744 rows copied from part_test_6
NOTICE: 720 rows copied from part_test_7
NOTICE: 744 rows copied from part_test_8
NOTICE: 720 rows copied from part_test_9
NOTICE: 744 rows copied from part_test_10
NOTICE: 744 rows copied from part_test_11
NOTICE: 720 rows copied from part_test_12
NOTICE: 744 rows copied from part_test_13
NOTICE: 507 rows copied from part_test_14
NOTICE: 0 rows copied from part_test_15
NOTICE: 0 rows copied from part_test_16
NOTICE: 0 rows copied from part_test_17
NOTICE: 0 rows copied from part_test_18
NOTICE: 0 rows copied from part_test_19
NOTICE: 0 rows copied from part_test_20
NOTICE: 0 rows copied from part_test_21
NOTICE: 0 rows copied from part_test_22
NOTICE: 0 rows copied from part_test_23
NOTICE: 0 rows copied from part_test_24
NOTICE: 0 rows copied from part_test_25
NOTICE: 0 rows copied from part_test_26
NOTICE: 0 rows copied from part_test_27
drop_partitions
-----------------
24
(1 row)
postgres=# select count(*) from part_test;
count
-------
9256
(1 row)
postgres=# \dt part_test_4
No matching relations found.
10. 绑定分区(已有的表加入分区表)
将已有的表，绑定到已有的某个分区主表。
已有的表与主表要保持一致的结构，包括dropped columns。 (查看pg_attribute的一致性)
如果设置了回调函数，会触发。
接口如下
attach_range_partition(relation REGCLASS, -- 主表OID
partition REGCLASS, -- 分区表OID
start_value ANYELEMENT, -- 起始值
end_value ANYELEMENT) -- 结束值
例子
postgres=# create table part_test_1 (like part_test including all);
CREATE TABLE
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
postgres=# \d+ part_test_1
Table "public.part_test_1"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
postgres=# select attach_range_partition('part_test'::regclass, 'part_test_1'::regclass, '2019-01-01 00:00:00'::timestamp, '2019-02-01 00:00:00'::timestamp);
attach_range_partition
------------------------
part_test_1
(1 row)
绑定分区时，
自动创建继承关系，自动创建约束
postgres=# \d+ part_test_1
Table "public.part_test_1"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_1_3_check" CHECK (crt_time >= '2019-01-01 00:00:00'::timestamp without time zone AND crt_time < '2019-02-01 00:00:00'::timestamp without time zone)
Inherits: part_test
11. 解绑分区(将分区变成普通表)
将分区从主表的继承关系中删除, 不删数据，删除继承关系，删除约束
接口如下
detach_range_partition(partition REGCLASS) -- 指定分区名，转换为普通表
例子
postgres=# select count(*) from part_test;
count
-------
9256
(1 row)
postgres=# select count(*) from part_test_2;
count
-------
733
(1 row)
postgres=# select detach_range_partition('part_test_2');
detach_range_partition
------------------------
part_test_2
(1 row)
postgres=# select count(*) from part_test_2;
count
-------
733
(1 row)
postgres=# select count(*) from part_test;
count
-------
8523
(1 row)
接口函数内容
postgres=# \sf detach_range_partition
CREATE OR REPLACE FUNCTION public.detach_range_partition(partition regclass)
RETURNS text
LANGUAGE plpgsql
AS $function$
DECLARE
v_attname TEXT;
parent_relid REGCLASS;
BEGIN
parent_relid := public.get_parent_of_partition(partition);
/* Acquire lock on parent */
PERFORM public.lock_partitioned_relation(parent_relid);
v_attname := attname
FROM public.pathman_config
WHERE partrel = parent_relid;
IF v_attname IS NULL THEN
RAISE EXCEPTION 'table "%" is not partitioned', parent_relid::TEXT;
END IF;
/* Remove inheritance */
EXECUTE format('ALTER TABLE %s NO INHERIT %s',
partition::TEXT,
parent_relid::TEXT);
/* Remove check constraint */
EXECUTE format('ALTER TABLE %s DROP CONSTRAINT %s',
partition::TEXT,
public.build_check_constraint_name(partition, v_attname));
/* Invalidate cache */
PERFORM public.on_update_partitions(parent_relid);
RETURN partition;
END
$function$
12. 更新触发器
如果分区字段要被更新，需要创建更新触发器，否则不需要。
接口函数如下
create_hash_update_trigger(parent REGCLASS)
Creates the trigger on UPDATE for HASH partitions.
The UPDATE trigger isn't created by default because of the overhead.
It's useful in cases when the key attribute might change.
create_range_update_trigger(parent REGCLASS)
Same as above, but for a RANGE-partitioned table.
例子
创建更新触发器前，如果更新分区字段后的值跨分区了，会报约束错误。
postgres=# select * from part_test_3 limit 10;
id | info | crt_time
-----+----------------------------------+----------------------------
734 | 52288de52fccf3d47efe897e1320a0fd | 2016-11-25 00:11:34.113856
735 | 16f4fffda933356192af8d1991c673cf | 2016-11-25 01:11:34.113862
736 | 08ec10184500ef43a6efde38dc43df33 | 2016-11-25 02:11:34.113867
737 | e658c7fb7f44ae3145401bf348cfa9dd | 2016-11-25 03:11:34.113872
738 | 81ff4c5cb3404230341aa95c28f86931 | 2016-11-25 04:11:34.113877
739 | 931652d6ba49f8155b1486d30fd23bab | 2016-11-25 05:11:34.113883
740 | c616c01d98016ff0022aa5449d53ca8f | 2016-11-25 06:11:34.113888
741 | 358e44b68259587233a0f571e8a86a81 | 2016-11-25 07:11:34.113893
742 | 719bb75e67c23c1f76e4eb81cb22004e | 2016-11-25 08:11:34.113899
743 | 1fc90c401eec2927fe9bb726651e4936 | 2016-11-25 09:11:34.113904
(10 rows)
postgres=# update part_test set crt_time='2016-01-25 00:11:34.113856' where id=734;
ERROR: new row for relation "part_test_3" violates check constraint "pathman_part_test_3_3_check"
DETAIL: Failing row contains (734, 52288de52fccf3d47efe897e1320a0fd, 2016-01-25 00:11:34.113856).
创建更新触发器后，正常
postgres=# select create_range_update_trigger('part_test'::regclass);
create_range_update_trigger
--------------------------------
public.part_test_upd_trig_func
(1 row)
postgres=# update part_test set crt_time='2016-01-25 00:11:34.113856' where id=734;
UPDATE 0
postgres=# select * from part_test where id=734;
id | info | crt_time
-----+----------------------------------+----------------------------
734 | 52288de52fccf3d47efe897e1320a0fd | 2016-01-25 00:11:34.113856
(1 row)
通常业务设计时，不应该允许分区字段的变更。
13. 永久禁止分区表pg_pathman插件
你可以针对单个分区主表禁用pg_pathman。
接口函数如下
disable_pathman_for(relation TEXT)
Permanently disable pg_pathman partitioning mechanism for the specified parent table and remove the insert trigger if it exists.
All partitions and data remain unchanged.
postgres=# \sf disable_pathman_for
CREATE OR REPLACE FUNCTION public.disable_pathman_for(parent_relid regclass)
RETURNS void
LANGUAGE plpgsql
STRICT
AS $function$
BEGIN
PERFORM public.validate_relname(parent_relid);
DELETE FROM public.pathman_config WHERE partrel = parent_relid;
PERFORM public.drop_triggers(parent_relid);
/* Notify backend about changes */
PERFORM public.on_remove_partitions(parent_relid);
END
$function$
例子
postgres=# select disable_pathman_for('part_test');
NOTICE: drop cascades to 23 other objects
DETAIL: drop cascades to trigger part_test_upd_trig on table part_test_3
drop cascades to trigger part_test_upd_trig on table part_test_4
drop cascades to trigger part_test_upd_trig on table part_test_5
drop cascades to trigger part_test_upd_trig on table part_test_6
drop cascades to trigger part_test_upd_trig on table part_test_7
drop cascades to trigger part_test_upd_trig on table part_test_8
drop cascades to trigger part_test_upd_trig on table part_test_9
drop cascades to trigger part_test_upd_trig on table part_test_10
drop cascades to trigger part_test_upd_trig on table part_test_11
drop cascades to trigger part_test_upd_trig on table part_test_12
drop cascades to trigger part_test_upd_trig on table part_test_13
drop cascades to trigger part_test_upd_trig on table part_test_14
drop cascades to trigger part_test_upd_trig on table part_test_15
drop cascades to trigger part_test_upd_trig on table part_test_16
drop cascades to trigger part_test_upd_trig on table part_test_17
drop cascades to trigger part_test_upd_trig on table part_test_18
drop cascades to trigger part_test_upd_trig on table part_test_19
drop cascades to trigger part_test_upd_trig on table part_test_20
drop cascades to trigger part_test_upd_trig on table part_test_21
drop cascades to trigger part_test_upd_trig on table part_test_22
drop cascades to trigger part_test_upd_trig on table part_test_23
drop cascades to trigger part_test_upd_trig on table part_test_24
drop cascades to trigger part_test_upd_trig on table part_test_25
disable_pathman_for
---------------------
(1 row)
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_10,
part_test_11,
part_test_12,
part_test_13,
part_test_14,
part_test_15,
part_test_16,
part_test_17,
part_test_18,
part_test_19,
part_test_20,
part_test_21,
part_test_22,
part_test_23,
part_test_24,
part_test_25,
part_test_26,
part_test_27,
part_test_28,
part_test_29,
part_test_3,
part_test_30,
part_test_31,
part_test_32,
part_test_33,
part_test_34,
part_test_35,
part_test_4,
part_test_5,
part_test_6,
part_test_7,
part_test_8,
part_test_9
postgres=# \d+ part_test_10
Table "public.part_test_10"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_10_3_check" CHECK (crt_time >= '2017-06-25 00:00:00'::timestamp without time zone AND crt_time < '2017-07-25 00:00:00'::timestamp without time zone)
Inherits: part_test
禁用pg_pathman后，继承关系和约束不会变化，只是pg_pathman不介入custom scan 执行计划。
禁用pg_pathman后的执行计划
postgres=# explain select * from part_test where crt_time='2017-06-25 00:00:00'::timestamp;
QUERY PLAN
---------------------------------------------------------------------------------
Append (cost=0.00..16.00 rows=2 width=45)
-> Seq Scan on part_test (cost=0.00..0.00 rows=1 width=45)
Filter: (crt_time = '2017-06-25 00:00:00'::timestamp without time zone)
-> Seq Scan on part_test_10 (cost=0.00..16.00 rows=1 width=45)
Filter: (crt_time = '2017-06-25 00:00:00'::timestamp without time zone)
(5 rows)
disable_pathman_for没有可逆操作，请慎用。
14. 全局禁止pg_pathman
与禁用单个分区主表不同，全局禁止只需要调整参数即可，不需要修改pg_pathman的元数据，同时它是可逆操作。
pg_pathman.enable
例子
$ vi $PGDATA/postgresql.conf
pg_pathman.enable = off
$ pg_ctl reload
分区表高级管理
1. 禁用主表
当主表的数据全部迁移到分区后，可以禁用主表。
接口函数如下
set_enable_parent(relation REGCLASS, value BOOLEAN)
Include/exclude parent table into/from query plan.
In original PostgreSQL planner parent table is always included into query plan even if it's empty which can lead to additional overhead.
You can use disable_parent() if you are never going to use parent table as a storage.
Default value depends on the partition_data parameter that was specified during initial partitioning in create_range_partitions() or create_partitions_from_range() functions.
If the partition_data parameter was true then all data have already been migrated to partitions and parent table disabled.
Otherwise it is enabled.
例子
select set_enable_parent('part_test', false);
2. 自动扩展分区
范围分区表，允许自动扩展分区。
如果新插入的数据不在已有的分区范围内，会自动创建分区。
set_auto(relation REGCLASS, value BOOLEAN)
Enable/disable auto partition propagation (only for RANGE partitioning).
It is enabled by default.
例子
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_10,
part_test_11,
part_test_12,
part_test_13,
part_test_14,
part_test_15,
part_test_16,
part_test_17,
part_test_18,
part_test_19,
part_test_20,
part_test_21,
part_test_22,
part_test_23,
part_test_24,
part_test_25,
part_test_26,
part_test_3,
part_test_4,
part_test_5,
part_test_6,
part_test_7,
part_test_8,
part_test_9
postgres=# \d+ part_test_26
Table "public.part_test_26"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_26_3_check" CHECK (crt_time >= '2018-09-25 00:00:00'::timestamp without time zone AND crt_time < '2018-10-25 00:00:00'::timestamp without time zone)
Inherits: part_test
postgres=# \d+ part_test_25
Table "public.part_test_25"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Check constraints:
"pathman_part_test_25_3_check" CHECK (crt_time >= '2018-08-25 00:00:00'::timestamp without time zone AND crt_time < '2018-09-25 00:00:00'::timestamp without time zone)
Inherits: part_test
插入一个不在已有分区范围的值，会根据创建分区时的interval自动扩展若干个分区，这个操作可能很久很久。
postgres=# insert into part_test values (1,'test','2222-01-01'::timestamp);
等了很久
21298 digoal 20 0 93.1g 184m 127m R 98.7 0.1 0:33.34 postgres: bgworker: SpawnPartitionsWorker
插入结束后，扩展了好多好多分区，原因是插入的值跨度范围太大了。
postgres=# \d+ part_test
Table "public.part_test"
Column | Type | Modifiers | Storage | Stats target | Description
----------+-----------------------------+-----------+----------+--------------+-------------
id | integer | | plain | |
info | text | | extended | |
crt_time | timestamp without time zone | not null | plain | |
Child tables: part_test_10,
part_test_100,
part_test_1000,
part_test_1001,
.....................................
很多
不建议开启自动扩展范围分区
3. 回调函数 (创建每个分区时都会触发)
回调函数是在每创建一个分区时会自动触发调用的函数。
例如可以用在ddl逻辑复制中，将DDL语句记录下来，存放到表中。
回调函数如下
set_init_callback(relation REGCLASS, callback REGPROC DEFAULT 0)
Set partition creation callback to be invoked for each attached or created partition (both HASH and RANGE).
The callback must have the following signature:
part_init_callback(args JSONB) RETURNS VOID.
Parameter arg consists of several fields whose presence depends on partitioning type:
/* RANGE-partitioned table abc (child abc_4) */
{
"parent": "abc",
"parttype": "2",
"partition": "abc_4",
"range_max": "401",
"range_min": "301"
}
/* HASH-partitioned table abc (child abc_0) */
{
"parent": "abc",
"parttype": "1",
"partition": "abc_0"
}
例子
回调函数
postgres=# create or replace function f_callback_test(jsonb) returns void as
$$
declare
begin
create table if not exists rec_part_ddl(id serial primary key, parent name, parttype int, partition name, range_max text, range_min text);
if ($1->>'parttype')::int = 1 then
raise notice 'parent: %, parttype: %, partition: %', $1->>'parent', $1->>'parttype', $1->>'partition';
insert into rec_part_ddl(parent, parttype, partition) values (($1->>'parent')::name, ($1->>'parttype')::int, ($1->>'partition')::name);
elsif ($1->>'parttype')::int = 2 then
raise notice 'parent: %, parttype: %, partition: %, range_max: %, range_min: %', $1->>'parent', $1->>'parttype', $1->>'partition', $1->>'range_max', $1->>'range_min';
insert into rec_part_ddl(parent, parttype, partition, range_max, range_min) values (($1->>'parent')::name, ($1->>'parttype')::int, ($1->>'partition')::name, $1->>'range_max', $1->>'range_min');
end if;
end;
$$ language plpgsql strict;
测试表
postgres=# create table tt(id int, info text, crt_time timestamp not null);
CREATE TABLE
设置测试表的回调函数
select set_init_callback('tt'::regclass, 'f_callback_test'::regproc);
创建分区
postgres=# select
create_range_partitions('tt'::regclass, -- 主表OID
'crt_time', -- 分区列名
'2016-10-25 00:00:00'::timestamp, -- 开始值
interval '1 month', -- 间隔；interval 类型，用于时间分区表
24, -- 分多少个区
false) ;
create_range_partitions
-------------------------
24
(1 row)
检查回调函数是否已调用
postgres=# select * from rec_part_ddl;
id | parent | parttype | partition | range_max | range_min
----+--------+----------+-----------+---------------------+---------------------
1 | tt | 2 | tt_1 | 2016-11-25 00:00:00 | 2016-10-25 00:00:00
2 | tt | 2 | tt_2 | 2016-12-25 00:00:00 | 2016-11-25 00:00:00
3 | tt | 2 | tt_3 | 2017-01-25 00:00:00 | 2016-12-25 00:00:00
4 | tt | 2 | tt_4 | 2017-02-25 00:00:00 | 2017-01-25 00:00:00
5 | tt | 2 | tt_5 | 2017-03-25 00:00:00 | 2017-02-25 00:00:00
6 | tt | 2 | tt_6 | 2017-04-25 00:00:00 | 2017-03-25 00:00:00
7 | tt | 2 | tt_7 | 2017-05-25 00:00:00 | 2017-04-25 00:00:00
8 | tt | 2 | tt_8 | 2017-06-25 00:00:00 | 2017-05-25 00:00:00
9 | tt | 2 | tt_9 | 2017-07-25 00:00:00 | 2017-06-25 00:00:00
10 | tt | 2 | tt_10 | 2017-08-25 00:00:00 | 2017-07-25 00:00:00
11 | tt | 2 | tt_11 | 2017-09-25 00:00:00 | 2017-08-25 00:00:00
12 | tt | 2 | tt_12 | 2017-10-25 00:00:00 | 2017-09-25 00:00:00
13 | tt | 2 | tt_13 | 2017-11-25 00:00:00 | 2017-10-25 00:00:00
14 | tt | 2 | tt_14 | 2017-12-25 00:00:00 | 2017-11-25 00:00:00
15 | tt | 2 | tt_15 | 2018-01-25 00:00:00 | 2017-12-25 00:00:00
16 | tt | 2 | tt_16 | 2018-02-25 00:00:00 | 2018-01-25 00:00:00
17 | tt | 2 | tt_17 | 2018-03-25 00:00:00 | 2018-02-25 00:00:00
18 | tt | 2 | tt_18 | 2018-04-25 00:00:00 | 2018-03-25 00:00:00
19 | tt | 2 | tt_19 | 2018-05-25 00:00:00 | 2018-04-25 00:00:00
20 | tt | 2 | tt_20 | 2018-06-25 00:00:00 | 2018-05-25 00:00:00
21 | tt | 2 | tt_21 | 2018-07-25 00:00:00 | 2018-06-25 00:00:00
22 | tt | 2 | tt_22 | 2018-08-25 00:00:00 | 2018-07-25 00:00:00
23 | tt | 2 | tt_23 | 2018-09-25 00:00:00 | 2018-08-25 00:00:00
24 | tt | 2 | tt_24 | 2018-10-25 00:00:00 | 2018-09-25 00:00:00
(24 rows)
