Postgres 顺序错误答案

【问题标题】：Postgres order by in wrong orderPostgres 顺序错误
【发布时间】：2019-03-24 18:34:43
【问题描述】：

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。它没有正确排序。

我使用 Python 和 psycopg2 将解析结果保存在 Postgres 中，然后指出，我无法测试排序，导致 Postgres return order by 出现错误。

更新：复制：

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 (Debian 6.3.0-18+deb9u) 编译 1) 6.3.0 20170516, 64位

【问题讨论】：

":" 小于 "s" 所以它排序正确（http: 应该在所有 https: 之前）。
@thebjorn 一开始我也这么认为，但是底部有两行以“http”开头。
编辑您的问题，并粘贴 create table、insert 和 select 语句来重现您的问题。
标记 Postgres 版本。使用您的复制有限集显示结果（所以 4 行而不是 33 行）。无论如何，对我有用，Postgres 11.1。
排序没有问题：有些排序规则会忽略非字母或数字的字符。

标签： postgresql postgresql-11

【解决方案1】：

假设您使用的是 UTF8 编码，指定排序规则而不是接受默认值应该可以解决您的直接问题。这是否是正确的事情取决于应用程序。

有几种不同的方式来指定排序规则。您可以在初始化数据库集群、创建数据库、运行查询等时指定它。有关更多详细信息，请参阅文档中的Collation support。

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

【讨论】：