--pg支持范围类型

• int4range — Range of integer

• int8range — Range of bigint

• numrange — Range of numeric

• tsrange — Range of timestamp without time zone

• tstzrange — Range of timestamp with time zone

• daterange — Range of date

--范围时间戳

CREATE TABLE reservation (room int, during tsrange);

--插入范围内时间

INSERT INTO reservation VALUES

(1108, '[2010-01-01 14:30, 2010-01-01 15:30)');

 --正无空大，负无穷小 -infinity 代表无穷小

 INSERT INTO reservation VALUES

(1109, '[2010-01-01 14:30,"infinity" )'),(1110, '["-infinity",2010-01-01 14:30)');

postgres=# select * from reservation ;

 room |                    during                     

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

 1108 | ["2010-01-01 14:30:00","2010-01-01 15:30:00")

 1109 | ["2010-01-01 14:30:00",infinity)

 1110 | [-infinity,"2010-01-01 14:30:00")

 

 -- Containment 范围内是否包含某一个值

SELECT int4range(10, 20) @> 3;

-- Overlaps 两个范围是否有重叠

SELECT numrange(11.1, 22.2) && numrange(20.0, 30.0);

-- Extract the upper bound 求范围的上限

SELECT upper(int8range(15, 25));

-- Compute the intersection 求两个范围的交集

SELECT int4range(10, 20) * int4range(15, 25);

-- Is the range empty? 判断范围是否为空

SELECT isempty(numrange(1, 5));

--每个范围类型都有一个与对应的构造函数，注意第三个参数说明其是全包围还是半包围

postgres=# SELECT int8range(1, 14, '(]');

 int8range 

-----------

 [2,15)

postgres=# SELECT numrange(NULL, 2.2);

 numrange 

----------

 (,2.2)

 

--用户也可以自定义范围类型，注意如果想要更好的使用GiST or SP-GiST索引，则需要定义一个差异化函数

--差异化函数要返回一个float8的值，并且其结果不能受字符集和排序规则的影响

--The subtype difference function takes two input values of the subtype, and returns their difference (i.e., X minus Y) represented as a float8 value

--the subtype_diff function should agree with the sort ordering implied by the selected operator class and collation

--创建差异化函数

CREATE FUNCTION time_subtype_diff(x time, y time) RETURNS float8 AS

'SELECT EXTRACT(EPOCH FROM (x - y))' LANGUAGE sql STRICT IMMUTABLE;

--创建自定义的范围类型

CREATE TYPE timerange AS RANGE (

subtype = time,

subtype_diff = time_subtype_diff

);

postgres=# SELECT '[11:10, 23:00]'::timerange;

      timerange      

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

 [11:10:00,23:00:00]

 

 

 --可以对范围类型的表列创建 GiST 和 SP-GiST 索引。

 --虽然对范围类型的表列可以创建 B-tree 和哈希索引，但不建议使用

 --There is a B-tree sort ordering defined for range values, with corresponding < and > operators, but the ordering is rather arbitrary and not usually useful in the real world

CREATE INDEX reservation_idx ON reservation USING gist (during);