PostgreSQL数组使用

开发的语言有数组的概念，对应于postgresql也有相关的数据字段类型，数组是英文array的翻译，可以定义一维，二维甚至更多维度，数学上跟矩阵很类似。在postgres里面可以直接存储使用，某些场景下使用很方便，也很强大。

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:

[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 | {3,5}
  3 | {6,9}
(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 | {1,55,99,66}
(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 | {55,1,66}
(1 row)

d.数据查询

postgres=# insert into t_kenyon(items) values('{3,5}');
INSERT 0 1

postgres=# select * from t_kenyon where id = 1;
id |        items       
----+---------------------
  1 | {55,66}
(1 row)

postgres=# select * from t_kenyon where items[1] = 55;
id |        items       
----+---------------------
  1 | {55,66}
(1 row)

postgres=# select * from t_kenyon where items[3] = 5;
id |  items 
----+---------
  4 | {3,5}
(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[1,3] <= ARRAY[1,3];
?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      
-------------------
{{11,34}}
(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,'{1,3}'); INSERT 0 1 postgres=# insert into t_kenyon values(1,'{2,4}'); INSERT 0 1 postgres=# insert into t_kenyon values(1,'{34,8}'); 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[1,3]	t
<>	not equal	ARRAY[1,3] <> ARRAY[1,4]	<	less than	>	greater than	<=	less than or equal	>=	greater than or equal	@>	contains	<@	is contained by	ARRAY[2,7] <@ ARRAY[1,6]	&&	overlap (have elements in common)	\|\|	array-to-array concatenation	ARRAY[1,3] \|\| ARRAY[4,5,239)"> {1,3,6}
\|\|	array-to-array concatenation	{{1,3},{4,6},{7,9}}
element-to-array concatenation	3 \|\| ARRAY[4,248)">{3,248)">array-to-element concatenation	ARRAY[4,6] \|\| 7	{4,6,7}

数组函数：
Function Return Type array_append(anyarray,anyelement) anyarray append an element to the end of an array array_append(ARRAY[1,3) {1,3} array_cat(anyarray,anyarray) anyarray concatenate two arrays array_cat(ARRAY[1,3],ARRAY[4,5]) array_ndims(anyarray) int returns the number of dimensions of the array array_ndims(ARRAY[[1,[4,6]]) 2 array_dims(anyarray) text returns a text representation of array's dimensions array_dims(ARRAY[[1,248)">[1:2][1:3] array_fill(anyelement,int[],[,int[]]) returns an array initialized with supplied value and dimensions,optionally with lower bounds other than 1 array_fill(7,ARRAY[3],ARRAY[2]) [2:4]={7,7} array_length(anyarray,int) returns the length of the requested array dimension array_length(array[1,1) 3 array_lower(anyarray,248)">returns lower bound of the requested array dimension array_lower('[0:2]={1,3}'::int[],248)">0 array_prepend(anyelement,248)">append an element to the beginning of an array array_prepend(1,ARRAY[2,3]) array_to_string(anyarray,text[,text]) concatenates array elements using supplied delimiter and optional null string array_to_string(ARRAY[1,NULL,5],','*') 1,*,5 array_upper(anyarray,248)">returns upper bound of the requested array dimension array_upper(ARRAY[1,7],248)">4 string_to_array(text,248)">text[] splits string into array elements using supplied delimiter and optional null string string_to_array('xx~^~yy~^~zz','~^~','yy') {xx,zz} unnest(anyarray) setof anyelement expand an array to a set of rows unnest(ARRAY[1,2])

1
2

(2 rows)
参考：http://www.postgresql.org/docs/9.2/static/functions-array.html

PostgreSQL数组使用

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