該博文用於自己學習記錄，內容節選自： https://github.com/digoal/blog/blob/master/201610/20161024_01.md
pg_pathman 創建分區表時，需要指定主表的名字，主表必須已存在，主表可以有數據，也可以是空表。
如果主表有數據，那么可以配置是否需要在創建分區時，將數據遷移到分區，（不建議對大表這么做）。
如果主表有很多數據，建議使用后台非堵塞式的遷移方法。 （調用partition_table_concurrently()函數進行遷移）。
如果在創建分區表前，使用set_init_callback(relation regclass, callback regproc DEFAULT 0)設置了回調函數，則創建分區時，每個分區表創建是，會自動調用對應的回調函數。
回調函數的傳入參數和模式如下
$part_init_callback$(args JSONB) RETURNS VOID
傳入參數如下
/* 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分區
有4個管理函數用來創建范圍分區
指定起始值、間隔、分區個數
create_range_partitions(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分區列名
start_value ANYELEMENT, -- 開始值
p_interval ANYELEMENT, -- 間隔；任意類型，適合任意類型的分區表
p_count INTEGER DEFAULT NULL, -- 分多少個區
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即將數據從主表遷移到分區, 不建議這么使用, 建議使用非堵塞式的遷移( 調用partition_table_concurrently() )
create_range_partitions(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分區列名
start_value ANYELEMENT, -- 開始值
p_interval INTERVAL, -- 間隔；interval 類型，用於時間分區表
p_count INTEGER DEFAULT NULL, -- 分多少個區
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即將數據從主表遷移到分區, 不建議這么使用, 建議使用非堵塞式的遷移( 調用partition_table_concurrently() )
指定起始值、終值、間隔
create_partitions_from_range(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分區列名
start_value ANYELEMENT, -- 開始值
end_value ANYELEMENT, -- 結束值
p_interval ANYELEMENT, -- 間隔；任意類型，適合任意類型的分區表
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即將數據從主表遷移到分區, 不建議這么使用, 建議使用非堵塞式的遷移( 調用partition_table_concurrently() )
create_partitions_from_range(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分區列名
start_value ANYELEMENT, -- 開始值
end_value ANYELEMENT, -- 結束值
p_interval INTERVAL, -- 間隔；interval 類型，用於時間分區表
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即將數據從主表遷移到分區, 不建議這么使用, 建議使用非堵塞式的遷移( 調用partition_table_concurrently() )
例子
創建需要分區的主表 postgres=# create table part_test(id int, info text, crt_time timestamp not null); -- 分區列必須有not null約束
CREATE TABLE 插入一批測試數據，模擬已經有數據了的主表 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. 分區列必須有not null約束 2. 分區個數必須能覆蓋已有的所有記錄 創建分區，每個分區包含1個月的跨度數據 postgres=# select create_range_partitions('part_test'::regclass, -- 主表OID
'crt_time', -- 分區列名
'2016-10-25 00:00:00'::timestamp, -- 開始值
interval '1 month', -- 間隔；interval 類型，用於時間分區表
24, -- 分多少個區
false) ; -- 不遷移數據
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 由於不遷移數據，所以數據還在主表 postgres=# select count(*) from only part_test; count
-------
10000 (1 row) 使用非堵塞式的遷移接口 partition_table_concurrently(relation REGCLASS, -- 主表OID
batch_size INTEGER DEFAULT 1000, -- 一個事務批量遷移多少記錄
sleep_time FLOAT8 DEFAULT 1.0) -- 獲得行鎖失敗時，休眠多久再次獲取，重試60次退出任務。
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) 遷移結束后，主表數據已經沒有了，全部在分區中 postgres=# select count(*) from only part_test; count
-------
0 (1 row) 數據遷移完成后，建議禁用主表，這樣執行計划就不會出現主表了 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)
建議
1. 分區列必須有not null約束
2. 分區個數必須能覆蓋已有的所有記錄
3. 建議使用非堵塞式遷移接口
4. 建議數據遷移完成后，禁用主表
2. hash分區
有1個管理函數用來創建范圍分區
指定起始值、間隔、分區個數
create_hash_partitions(relation REGCLASS, -- 主表OID
attribute TEXT, -- 分區列名
partitions_count INTEGER, -- 打算創建多少個分區
partition_data BOOLEAN DEFAULT TRUE) -- 是否立即將數據從主表遷移到分區, 不建議這么使用, 建議使用非堵塞式的遷移( 調用partition_table_concurrently() )
例子
創建需要分區的主表 postgres=# create table part_test(id int, info text, crt_time timestamp not null); -- 分區列必須有not null約束
CREATE TABLE 插入一批測試數據，模擬已經有數據了的主表 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. 分區列必須有not null約束 創建128個分區 postgres=# select create_hash_partitions('part_test'::regclass, -- 主表OID
'crt_time', -- 分區列名
128, -- 打算創建多少個分區
false) ; -- 不遷移數據
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 由於不遷移數據，所以數據還在主表 postgres=# select count(*) from only part_test; count
-------
10000 (1 row) 使用非堵塞式的遷移接口 partition_table_concurrently(relation REGCLASS, -- 主表OID
batch_size INTEGER DEFAULT 1000, -- 一個事務批量遷移多少記錄
sleep_time FLOAT8 DEFAULT 1.0) -- 獲得行鎖失敗時，休眠多久再次獲取，重試60次退出任務。
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) 遷移結束后，主表數據已經沒有了，全部在分區中 postgres=# select count(*) from only part_test; count
-------
0 (1 row) 數據遷移完成后，建議禁用主表，這樣執行計划就不會出現主表了 postgres=# select set_enable_parent('part_test'::regclass, false); set_enable_parent -------------------
(1 row) 只查單個分區 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) 分區表約束如下 很顯然pg_pathman自動完成了轉換，如果是傳統的繼承，select * from part_test where crt_time = '2016-10-25 00:00:00'::timestamp; 這種寫法是不能篩選分區的。 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
建議
1. 分區列必須有not null約束
2. 建議使用非堵塞式遷移接口
3. 建議數據遷移完成后，禁用主表
4. pg_pathman不會受制於表達式的寫法，所以select * from part_test where crt_time = '2016-10-25 00:00:00'::timestamp;這樣的寫法也是能走哈希分區的。
5. hash分區列不局限於int類型的列，會使用hash函數自動轉換。
3. 數據遷移到分區
如果創建分區表時，未將主表數據遷移到分區，那么可以使用非堵塞式的遷移接口，將數據遷移到分區
可能類似如下做法
with tmp as (delete from 主表 limit xx nowait returning *) insert into 分區 select * from tmp
或者使用 select array_agg(ctid) from 主表 limit xx for update nowati 進行標示 然后執行delete和insert。
1. 函數接口如下
partition_table_concurrently(relation REGCLASS, -- 主表OID
batch_size INTEGER DEFAULT 1000, -- 一個事務批量遷移多少記錄
sleep_time FLOAT8 DEFAULT 1.0) -- 獲得行鎖失敗時，休眠多久再次獲取，重試60次退出任務。
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. 如何停止遷移任務，調用如下函數接口
stop_concurrent_part_task(relation REGCLASS)
4. 查看后台的數據遷移任務
postgres=# select * from pathman_concurrent_part_tasks; userid | pid | dbid | relid | processed | status --------+-----+------+-------+-----------+--------
(0 rows)
4. 分裂范圍分區
例如某個分區太大了，想分裂為兩個分區，可以使用這種方法
僅支持范圍分區表
split_range_partition(partition REGCLASS, -- 分區oid
split_value ANYELEMENT, -- 分裂值
partition_name TEXT DEFAULT NULL) -- 分裂后新增的分區表名
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, -- 分區oid
'2016-11-10 00:00:00'::timestamp, -- 分裂值
'part_test_1_2'); -- 分區表名
split_range_partition -----------------------------------------------
{"2016-10-25 00:00:00","2016-11-25 00:00:00"} (1 row)
分裂后的兩個表如下
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
數據會自動遷移到另一個分區
postgres=# select count(*) from part_test_1; count
-------
373 (1 row) postgres=# select count(*) from part_test_1_2; count
-------
360 (1 row)
繼承關系如下
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. 合並范圍分區
目前僅支持范圍分區
調用如下接口
指定兩個需要合並分區，必須為相鄰分區 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 不是相鄰分區，報錯 相鄰分區可以合並 postgres=# select merge_range_partitions('part_test_1'::regclass, 'part_test_1_2'::regclass) ; merge_range_partitions ------------------------
(1 row)
合並后，會刪掉其中一個分區表
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. 向后添加范圍分區
如果已經對主表進行了分區，將來需要增加分區的話，有幾種方法，一種是向后新增分區（即在末尾追加分區）。
新增分區時，會使用初次創建該分區表時的interval作為間隔。
可以在這個表中查詢每個分區表初次創建時的 interval
postgres=# select * from pathman_config; partrel | attname | parttype | range_interval -----------+----------+----------+----------------
part_test | crt_time | 2 | 1 mon (1 row)
添加分區接口，支持指定表空間
append_range_partition(parent REGCLASS, -- 主表OID
partition_name TEXT DEFAULT NULL, -- 新增的分區表名, 默認不需要輸入
tablespace TEXT DEFAULT NULL) -- 新增的分區表放到哪個表空間, 默認不需要輸入
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. 向前添加范圍分區
在頭部追加分區。
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. 添加分區
指定分區起始值的方式添加分區，只要創建的分區和已有分區不會存在數據交叉就可以創建成功。
也就是說使用這種方法，不要求強制創建連續的分區，例如已有分區覆蓋了2010-2015的范圍，你可以直接創建一個2020年的分區表，不需要覆蓋2015到2020的范圍。
接口如下
add_range_partition(relation REGCLASS, -- 主表OID
start_value ANYELEMENT, -- 起始值
end_value ANYELEMENT, -- 結束值
partition_name TEXT DEFAULT NULL, -- 分區名
tablespace TEXT DEFAULT NULL) -- 分區創建在哪個表空間下
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); -- 結束值
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. 刪除分區
1. 刪除單個范圍分區
接口如下
drop_range_partition(partition TEXT, -- 分區名稱
delete_data BOOLEAN DEFAULT TRUE) -- 是否刪除分區數據，如果false，表示分區數據遷移到主表。
Drop RANGE partition and all of its data if delete_data is true.
例子
刪除分區， 數據遷移到主表 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) 刪除分區，分區數據也刪除，不遷移到主表 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. 刪除所有分區，並且指定是否要將數據遷移到主表
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); -- 刪除所有分區表，並將數據遷移到主表
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. 綁定分區(已有的表加入分區表)
將已有的表，綁定到已有的某個分區主表。
已有的表與主表要保持一致的結構，包括dropped columns。 (查看pg_attribute的一致性)
如果設置了回調函數，會觸發。
接口如下
attach_range_partition(relation REGCLASS, -- 主表OID
partition REGCLASS, -- 分區表OID
start_value ANYELEMENT, -- 起始值
end_value ANYELEMENT) -- 結束值
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) 綁定分區時， 自動創建繼承關系，自動創建約束 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. 解綁分區(將分區變成普通表)
將分區從主表的繼承關系中刪除, 不刪數據，刪除繼承關系，刪除約束
接口如下
detach_range_partition(partition REGCLASS) -- 指定分區名，轉換為普通表
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)
接口函數內容
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. 更新觸發器
如果分區字段要被更新，需要創建更新觸發器，否則不需要。
接口函數如下
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
創建更新觸發器前，如果更新分區字段后的值跨分區了，會報約束錯誤。
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).
創建更新觸發器后，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)
通常業務設計時，不應該允許分區字段的變更。
13. 永久禁止分區表pg_pathman插件
你可以針對單個分區主表禁用pg_pathman。
接口函數如下
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，繼承關系和約束不會變化，只是pg_pathman不介入custom scan 執行計划。
禁用pg_pathman后的執行計划
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沒有可逆操作，請慎用。
14. 全局禁止pg_pathman
與禁用單個分區主表不同，全局禁止只需要調整參數即可，不需要修改pg_pathman的元數據，同時它是可逆操作。
pg_pathman.enable
例子
$ vi $PGDATA/postgresql.conf pg_pathman.enable = off $ pg_ctl reload
分區表高級管理
1. 禁用主表
當主表的數據全部遷移到分區后，可以禁用主表。
接口函數如下
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. 自動擴展分區
范圍分區表，允許自動擴展分區。
如果新插入的數據不在已有的分區范圍內，會自動創建分區。
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 插入一個不在已有分區范圍的值，會根據創建分區時的interval自動擴展若干個分區，這個操作可能很久很久。 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 插入結束后，擴展了好多好多分區，原因是插入的值跨度范圍太大了。 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
不建議開啟自動擴展范圍分區
3. 回調函數 (創建每個分區時都會觸發)
回調函數是在每創建一個分區時會自動觸發調用的函數。
例如可以用在ddl邏輯復制中，將DDL語句記錄下來，存放到表中。
回調函數如下
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
回調函數 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; 測試表 postgres=# create table tt(id int, info text, crt_time timestamp not null); CREATE TABLE 設置測試表的回調函數 select set_init_callback('tt'::regclass, 'f_callback_test'::regproc); 創建分區 postgres=# select create_range_partitions('tt'::regclass, -- 主表OID
'crt_time', -- 分區列名
'2016-10-25 00:00:00'::timestamp, -- 開始值
interval '1 month', -- 間隔；interval 類型，用於時間分區表
24, -- 分多少個區
false) ; create_range_partitions -------------------------
24 (1 row) 檢查回調函數是否已調用 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)