postgresql – 运算符〜<〜在Postgres中

@H_404_1@

(最初是 this question的一部分,但它有点无关紧要,所以我决定把它作为自己的问题.)

我找不到运算符〜<〜是什么. Postgres手册仅提及〜和类似的运算符here,但没有〜<〜的迹象. 在psql控制台中摆弄时,我发现这些命令会产生相同的结果：

SELECT * FROM test ORDER BY name USING ~<~;
SELECT * FROM test ORDER BY name COLLATE "C";

这些给出了相反的顺序：

SELECT * FROM test ORDER BY name USING ~>~;
SELECT * FROM test ORDER BY name COLLATE "C" DESC;

还有关于代字号运算符的一些信息：

\do ~*~
                                    List of operators
  Schema   | Name | Left arg type | Right arg type | Result type |       Description       
------------+------+---------------+----------------+-------------+-------------------------
pg_catalog | ~<=~ | character     | character      | boolean     | less than or equal
pg_catalog | ~<=~ | text          | text           | boolean     | less than or equal
pg_catalog | ~<~  | character     | character      | boolean     | less than
pg_catalog | ~<~  | text          | text           | boolean     | less than
pg_catalog | ~>=~ | character     | character      | boolean     | greater than or equal
pg_catalog | ~>=~ | text          | text           | boolean     | greater than or equal
pg_catalog | ~>~  | character     | character      | boolean     | greater than
pg_catalog | ~>~  | text          | text           | boolean     | greater than
pg_catalog | ~~   | bytea         | bytea          | boolean     | matches LIKE expression
pg_catalog | ~~   | character     | text           | boolean     | matches LIKE expression
pg_catalog | ~~   | name          | text           | boolean     | matches LIKE expression
pg_catalog | ~~   | text          | text           | boolean     | matches LIKE expression
(12 rows)

第3行和第4行是我正在寻找的运算符,但描述对我来说有点不足.

解决方法

〜> =〜,〜< =〜,〜>〜和〜<〜是文本模式(或varchar,基本相同)运算符,它们各自的兄弟姐妹的对应物> =,< =,>和<.他们严格按字节值对字符数据进行排序,忽略任何整理设置的规则(与其兄弟姐妹相对).这使它们更快,但对大多数语言/国家也无效. “C”语言环境实际上与没有语言环境相同,这意味着没有排序规则.这解释了为什么ORDER BY name USING~<〜和ORDER BY name COLLATE“C”最终做同样的事情. 关于dba.SE的相关答案的最后一章的详细说明：
> Pattern matching with LIKE,SIMILAR TO or regular expressions in PostgreSQL

注意~~是用于实现SQL LIKE expression的Postgres运算符,与上述几乎没有关系.同样,~~ *实现了ILIKE.更多：

> ~~ Operator In Postgres
> Symfony2 Doctrine – ILIKE clause for PostgreSQL?
> PostgreSQL – text Array contains value similar to