PostgreSQL Partition

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Table Partitions



1. Range
2. List
3. Hash    -->Support PostgreSQL 11
4. Table Inheritance



partition 10 and 11 difference:

1. Update Moves Rows Across Partitions
2. Create Default Partitions
3. Automatic Index Creation
4. Foreign Key Support
5. Unique Indexes


============================================================

RANGE PARTITION:

postgres=# create table rparent(id int,name text,doj date) partition by range(doj);
CREATE TABLE
postgres=# create table rc1 partition of rparent for values from ('01-jan-2011') to ('01-jan-2012');
CREATE TABLE
postgres=# create table rc2 partition of rparent for values from ('01-jan-2012') to ('01-jan-2013');
CREATE TABLE
postgres=# create table rc2 partition of rparent for values from ('01-jan-2013') to (maxvalue);
ERROR:  relation "rc2" already exists
postgres=# create table rc3 partition of rparent for values from ('01-jan-2013') to (maxvalue);
CREATE TABLE
postgres=# insert into rparent values (1,'aaa','21-may-2011')
postgres-# ;
INSERT 0 1
postgres=# insert into rparent values (2,'bbb','01-jun-2012')
postgres-# ;
INSERT 0 1
postgres=# insert into rparent values (3,'ccc','01-jun-2020');
;
INSERT 0 1
postgres=# select * from rparent ;
 id | name |    doj   
----+------+------------
  1 | aaa  | 2011-05-21
  2 | bbb  | 2012-06-01
  3 | ccc  | 2020-06-01
(3 rows)

postgres=# select * from rc1;
 id | name |    doj   
----+------+------------
  1 | aaa  | 2011-05-21
(1 row)

postgres=# select * from rc2;
 id | name |    doj   
----+------+------------
  2 | bbb  | 2012-06-01
(1 row)

postgres=# select * from rc3;
 id | name |    doj   
----+------+------------
  3 | ccc  | 2020-06-01
(1 row)

postgres=# \dt+
                      List of relations
 Schema |  Name   | Type  |  Owner   |  Size   | Description
--------+---------+-------+----------+---------+-------------
 public | rc1     | table | postgres | 16 kB   |
 public | rc2     | table | postgres | 16 kB   |
 public | rc3     | table | postgres | 16 kB   |
 public | rparent | table | postgres | 0 bytes |
 public | t1      | table | postgres | 4360 kB |
 public | t2      | table | postgres | 4360 kB |
(6 rows)

postgres=# drop table rparent ;
DROP TABLE
postgres=# \dt+
                    List of relations
 Schema | Name | Type  |  Owner   |  Size   | Description
--------+------+-------+----------+---------+-------------
 public | t1   | table | postgres | 4360 kB |
 public | t2   | table | postgres | 4360 kB |
(2 rows)

============================================================
LIST PARTITION:

postgres=# create table lparent(id int,name text,place text)partition by list(place);
CREATE TABLE
postgres=# create table lc1 partition of lparent for values in ('chennai');
CREATE TABLE
postgres=# create table lc2 partition of lparent for values in ('madurai','theni');
CREATE TABLE
postgres=# create table lc3 partition of lparent default;
CREATE TABLE
postgres=# insert into lparent values (1,'aaa','chennai');
INSERT 0 1
postgres=# insert into lparent values (1,'aaa','madurai');
INSERT 0 1
postgres=# insert into lparent values (1,'aaa','theni');
INSERT 0 1
postgres=# insert into lparent values (1,'aaa','covai');
INSERT 0 1
postgres=# insert into lparent values (1,'aaa','thiruchy');
INSERT 0 1
postgres=# select * from lparent ;
 id | name |  place 
----+------+----------
  1 | aaa  | chennai
  1 | aaa  | madurai
  1 | aaa  | theni
  1 | aaa  | covai
  1 | aaa  | thiruchy
(5 rows)

postgres=# select * from lc1 ;
 id | name |  place 
----+------+---------
  1 | aaa  | chennai
(1 row)

postgres=# select * from lc2 ;
 id | name |  place 
----+------+---------
  1 | aaa  | madurai
  1 | aaa  | theni
(2 rows)

postgres=# select * from lc3 ;
 id | name |  place 
----+------+----------
  1 | aaa  | covai
  1 | aaa  | thiruchy
(2 rows)

postgres=# create index in_t on lparent (place);
CREATE INDEX
postgres=# \d+ lparent
                                  Table "public.lparent"
 Column |  Type   | Collation | Nullable | Default | Storage  | Stats target | Description
--------+---------+-----------+----------+---------+----------+--------------+-------------
 id     | integer |           |          |         | plain    |              |
 name   | text    |           |          |         | extended |              |
 place  | text    |           |          |         | extended |              |
Partition key: LIST (place)
Indexes:
    "in_t" btree (place)
Partitions: lc1 FOR VALUES IN ('chennai'),
            lc2 FOR VALUES IN ('madurai', 'theni'),
            lc3 DEFAULT

========================================================================

HASH PARTITION:

postgres=# create table hparent (id int,name text) partition by hash(id);
CREATE TABLE
postgres=# create table hc1 partition of hparent for values with (MODULUS 3, REMAINDER 0);
CREATE TABLE
postgres=# create table hc2 partition of hparent for values with (MODULUS 3, REMAINDER 1);
CREATE TABLE
postgres=# create table hc3 partition of hparent for values with (MODULUS 3, REMAINDER 2);
CREATE TABLE
postgres=# INSERT INTO hparent values (generate_series(1,20),'asas');
INSERT 0 20
postgres=# select * from hparent ;
 id | name
----+------
  2 | asas
  4 | asas
  6 | asas
  8 | asas
 15 | asas
 16 | asas
 18 | asas
 19 | asas
 20 | asas
  3 | asas
  7 | asas
 10 | asas
 13 | asas
 14 | asas
  1 | asas
  5 | asas
  9 | asas
 11 | asas
 12 | asas
 17 | asas
(20 rows)

postgres=# select * from hc1 ;
 id | name
----+------
  2 | asas
  4 | asas
  6 | asas
  8 | asas
 15 | asas
 16 | asas
 18 | asas
 19 | asas
 20 | asas
(9 rows)

postgres=# select * from hc2 ;
 id | name
----+------
  3 | asas
  7 | asas
 10 | asas
 13 | asas
 14 | asas
(5 rows)

postgres=# select * from hc3 ;
 id | name
----+------
  1 | asas
  5 | asas
  9 | asas
 11 | asas
 12 | asas
 17 | asas
(6 rows)

postgres=# \dt+
                      List of relations
 Schema |  Name   | Type  |  Owner   |  Size   | Description
--------+---------+-------+----------+---------+-------------
 public | hc1     | table | postgres | 16 kB   |
 public | hc2     | table | postgres | 16 kB   |
 public | hc3     | table | postgres | 16 kB   |
 public | hparent | table | postgres | 0 bytes |
 public | lc1     | table | postgres | 16 kB   |
 public | lc2     | table | postgres | 16 kB   |
 public | lc3     | table | postgres | 16 kB   |
 public | lparent | table | postgres | 0 bytes |
 public | t1      | table | postgres | 4360 kB |
 public | t2      | table | postgres | 4360 kB |
(10 rows)
========================================================================

TABLE INHERITS:

postgres=# create table iparent(id int,name text);
CREATE TABLE
postgres=# create table ic1(id int,name text,age int)inherits(iparent);
NOTICE:  merging column "id" with inherited definition
NOTICE:  merging column "name" with inherited definition
CREATE TABLE
postgres=# create table ic2(id int,name text,dob date)inherits(iparent);
NOTICE:  merging column "id" with inherited definition
NOTICE:  merging column "name" with inherited definition
CREATE TABLE
postgres=# insert into iparent values (1,'sa');
INSERT 0 1
postgres=# insert into ic1 values (1,'sa',12);
INSERT 0 1
postgres=# insert into ic2 values (1,'sa','03-jan-2012');
INSERT 0 1
postgres=# select * from iparent ;
 id | name
----+------
  1 | sa
  1 | sa
  1 | sa
(3 rows)

postgres=# select * from ic1 ;
 id | name | age
----+------+-----
  1 | sa   |  12
(1 row)

postgres=# select * from ic2 ;
 id | name |    dob   
----+------+------------
  1 | sa   | 2012-01-03
(1 row)



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