postgresql - Postgres 排序顺序错误

Question

Postgres order by 得到错误的结果:

postgres=# SELECT (url) FROM posts_post ORDER BY url;
                                               url
--------------------------------------------------------------------------------------------------
 -----------------------------------------------------------------------------------------
 http://nautil.us/issue/70/variables/aging-is-a-communication-breakdown
 https://github.com/felixse/FluentTerminal
 http://www.bbc.com/future/story/20160408-the-ancient-peruvian-mystery-solved-from-space
 http://www.graffathon.fi/2016/presentations/additive_slides.pdf
(4 rows)

如您所见，“http://nautil.us/issue/70/variables/aging-is-a-communication-breakdown”有问题。它排序不正确。

我使用 Python 和 psycopg2 将解析结果保存在 Postgres 中，发现我无法测试排序，导致 Postgres 返回 order by 错误。

更新:重现:

CREATE TABLE test_post ("id" serial NOT NULL PRIMARY KEY, "title" text NOT NULL, "url" text NOT NULL, "created" timestamp with time zone NOT NULL);

INSERT INTO test_post (title, url, created) VALUES ('Aging Is', 'http://nautil.us/issue/70/variables/aging-is-a-communication-breakdown', NOW()) ON CONFLICT DO NOTHING;

INSERT INTO test_post (title, url, created) VALUES ('Untrusted – a user', 'https://github.com/felixse/FluentTerminal', NOW()) ON CONFLICT DO NOTHING;

INSERT INTO test_post (title, url, created) VALUES ('Artyping (1939)', 'http://www.bbc.com/future/story/20160408-the-ancient-peruvian-mystery-solved-from-space', NOW()) ON CONFLICT DO NOTHING;

INSERT INTO test_post (title, url, created) VALUES (' Applying the Universal', 'http://www.graffathon.fi/2016/presentations/additive_slides.pdf', NOW()) ON CONFLICT DO NOTHING;

SELECT (url) FROM test_post ORDER BY url;

x86_64-pc-linux-gnu 上的 PostgreSQL 11.2 (Debian 11.2-1.pgdg90+1)，由 gcc 编译 (Debian 6.3.0-18+deb9u1) 6.3.0 20170516，64位

Answer 1

假设您使用 UTF8 编码，指定排序规则而不是接受默认排序规则应该可以解决您眼前的问题。这是否正确取决于应用程序。

有几种不同的方法来指定排序规则。您可以在数据库集群初始化、创建数据库、运行查询等时指定它。请参阅 Collation support在文档中了解更多详细信息。

CREATE TABLE test_post (
    "id" serial NOT NULL PRIMARY KEY, 
    "title" text NOT NULL, 
    "url" text collate ucs_basic NOT NULL, 
    "created" timestamp with time zone NOT NULL
);

INSERT INTO test_post (title, url, created) VALUES 
('Aging Is', 'http://nautil.us/issue/70/variables/aging-is-a-communication-breakdown', NOW()) ON CONFLICT DO NOTHING;
INSERT INTO test_post (title, url, created) VALUES 
('Untrusted – a user', 'https://github.com/felixse/FluentTerminal', NOW()) ON CONFLICT DO NOTHING;
INSERT INTO test_post (title, url, created) VALUES 
('Artyping (1939)', 'http://www.bbc.com/future/story/20160408-the-ancient-peruvian-mystery-solved-from-space', NOW()) ON CONFLICT DO NOTHING;
INSERT INTO test_post (title, url, created) VALUES 
(' Applying the Universal', 'http://www.graffathon.fi/2016/presentations/additive_slides.pdf', NOW()) ON CONFLICT DO NOTHING;

SELECT (url) FROM test_post ORDER BY url;

http://nautil.us/issue/70/variables/aging-is-a-communication-breakdown
http://www.bbc.com/future/story/20160408-the-ancient-peruvian-mystery-solved-from-space
http://www.graffathon.fi/2016/presentations/additive_slides.pdf
https://github.com/felixse/FluentTerminal