Postgres数组使用

Postgres数组使用 环境： OS：CentOS 6.2 DB: PostgreSQL 9.2.4 1.数组的定义 不一样的维度元素长度定义在数据库中的实际存储都是一样的，数组元素的长度和类型必须要保持一致，并且以中括号来表示。 合理的： array[1,2] --一维数组 array[[1,2],[3,5]] --

Postgres数组使用

环境：

OS：CentOS 6.2

DB: PostgreSQL 9.2.4

1.数组的定义

不一样的维度元素长度定义在数据库中的实际存储都是一样的，数组元素的长度和类型必须要保持一致，并且以中括号来表示。

合理的：

array[1,2] --一维数组

array[[1,2],[3,5]] --二维数组 '{99,889}'

不合理的:

array[[1,2],[3]] --元素长度不一致

array[[1,2],['Kenyon','good']] --类型不匹配

[postgres@localhost ~]$ psql

psql (9.2.4)

Type "help" for help.

postgres=# create table t_kenyon(id serial primary key,items int[]);

NOTICE: CREATE TABLE will create implicit sequence "t_kenyon_id_seq" for serial column "t_kenyon.id"

NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t_kenyon_pkey" for table "t_kenyon"

CREATE TABLE

postgres=# \d+ t_kenyon

Table "public.t_kenyon"

Column | Type | Modifiers | Storage | Stats target | Description

--------+-----------+-------------------------------------------------------+----------+--------------+-------------

id | integer | not null default nextval('t_kenyon_id_seq'::regclass) | plain | |

items | integer[] | | extended | |

Indexes:

"t_kenyon_pkey" PRIMARY KEY, btree (id)

Has OIDs: no

postgres=# create table t_ken(id serial primary key,items int[4]);

NOTICE: CREATE TABLE will create implicit sequence "t_ken_id_seq" for serial column "t_ken.id"

NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t_ken_pkey" for table "t_ken"

CREATE TABLE

postgres=# \d+ t_ken

Table "public.t_ken"

Column | Type | Modifiers | Storage | Stats target | Description

--------+-----------+----------------------------------------------------+----------+--------------+-------------

id | integer | not null default nextval('t_ken_id_seq'::regclass) | plain | |

items | integer[] | | extended | |

Indexes:

"t_ken_pkey" PRIMARY KEY, btree (id)

Has OIDs: no

数组的存储方式是extended的。

2.数组操作

a.数据插入，有两种方式

postgres=# insert into t_kenyon(items) values('{1,2}');

INSERT 0 1

postgres=# insert into t_kenyon(items) values('{3,4,5}');

INSERT 0 1

postgres=# insert into t_kenyon(items) values(array[6,7,8,9]);

INSERT 0 1

postgres=# select * from t_kenyon;

id | items

----+-----------

1 | {1,2}

2 | {3,4,5}

3 | {6,7,8,9}

(3 rows)

b.数据删除

postgres=# delete from t_kenyon where id = 3;

DELETE 1

postgres=# delete from t_kenyon where items[1] = 4;

DELETE 0

postgres=# delete from t_kenyon where items[1] = 3;

DELETE 1

c.数据更新

往后追加

postgres=# update t_kenyon set items = items||7;

UPDATE 1

postgres=# select * from t_kenyon;

id | items

----+---------

1 | {1,2,7}

(1 row)

postgres=# update t_kenyon set items = items||'{99,66}';

UPDATE 1

postgres=# select * from t_kenyon;

id | items

----+------------------

1 | {1,2,7,55,99,66}

(1 row)

往前插

postgres=# update t_kenyon set items = array_prepend(55,items) ;

UPDATE 1

postgres=# select * from t_kenyon;

id | items

----+---------------------

1 | {55,1,2,7,55,99,66}

(1 row)

d.数据查询

postgres=# insert into t_kenyon(items) values('{3,4,5}');

INSERT 0 1

postgres=# select * from t_kenyon where id = 1;

id | items

----+---------------------

1 | {55,1,2,7,55,99,66}

(1 row)

postgres=# select * from t_kenyon where items[1] = 55;

id | items

----+---------------------

1 | {55,1,2,7,55,99,66}

(1 row)

postgres=# select * from t_kenyon where items[3] = 5;

id | items

----+---------

4 | {3,4,5}

(1 row)

postgres=# select items[1],items[3],items[4] from t_kenyon;

items | items | items

-------+-------+-------

55 | 2 | 7

3 | 5 |

(2 rows)

postgres=# select unnest(items) from t_kenyon where id = 4;

unnest

--------

3

4

5

(3 rows)

e.数组比较

postgres=# select ARRAY[1,2,3]

?column?

----------

t

(1 row)

f.数组字段类型转换

postgres=# select array[['11','12'],['23','34']]::int[];

array

-------------------

{{11,12},{23,34}}

(1 row)

postgres=# select array[[11,12],[23,34]]::text[];

array

-------------------

{{11,12},{23,34}}

(1 row)

3.数组索引

postgres=# create table t_kenyon(id int,items int[]);

CREATE TABLE

postgres=# insert into t_kenyon values(1,'{1,2,3}');

INSERT 0 1

postgres=# insert into t_kenyon values(1,'{2,4}');

INSERT 0 1

postgres=# insert into t_kenyon values(1,'{34,7,8}');

INSERT 0 1

postgres=# insert into t_kenyon values(1,'{99,12}');

INSERT 0 1

postgres=# create index idx_t_kenyon on t_kenyon using gin(items);

CREATE INDEX

postgres=# set enable_seqscan = off;

postgres=# explain select * from t_kenyon where items@>array[2];

QUERY PLAN

---------------------------------------------------------------------------

Bitmap Heap Scan on t_kenyon (cost=8.00..12.01 rows=1 width=36)

Recheck Cond: (items @> '{2}'::integer[])

-> Bitmap Index Scan on idx_t_kenyon (cost=0.00..8.00 rows=1 width=0)

Index Cond: (items @> '{2}'::integer[])

(4 rows)

附数组操作符:

Operator Description Example Result

= equal ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3] t

not equal ARRAY[1,2,3] ARRAY[1,2,4] t