Postgresql 数据库级别、table 级别、列级别的排序规则

Question

我使用 UTF8 字符集的排序规则类型 'C' 创建了数据库。如果我在同一数据库下创建任何 table 或索引，它将具有排序规则 'C' 或我需要在 table 或索引创建时明确定义。

我们如何提取 postgresql 11

中 table 和索引的整理细节

使用整理创建的数据库 'C' 还创建了 table 和没有明确整理类型的索引。

CREATE DATABASE testdb
    WITH 
    OWNER = postgres
    ENCODING = 'UTF8'
    LC_COLLATE = 'C'
    LC_CTYPE = 'en_US.UTF-8'
    TABLESPACE = testts
    CONNECTION LIMIT = -1
    TEMPLATE = template0;

create table test1c (id integer, content varchar(10));
create index idx_test on test1c(content);

需要有关 table 和索引级别整理的信息。

Answer 1

列的排序规则存储在列的 pg_attribute 行的 attcollation 中。值 100 表示“默认排序规则”，这是存储在 pg_database.

中的数据库排序规则

这是一种查找 table 所有列排序规则的方法：

WITH defcoll AS (
   SELECT datcollate AS coll
   FROM pg_database
   WHERE datname = current_database()
)
SELECT a.attname,
       CASE WHEN c.collname = 'default'
            THEN defcoll.coll
            ELSE c.collname
       END AS collation
FROM pg_attribute AS a
   CROSS JOIN defcoll
   LEFT JOIN pg_collation AS c ON a.attcollation = c.oid
WHERE a.attrelid = 'test1c'::regclass
  AND a.attnum > 0
ORDER BY attnum;

 attname | collation 
---------+-----------
 id      | 
 content | C
(2 rows)

对于索引，排序规则存储在列 pg_index.indcollation:

WITH defcoll AS (
   SELECT datcollate AS coll
   FROM pg_database
   WHERE datname = current_database()
)
SELECT icol.pos,
       CASE WHEN c.collname = 'default'
            THEN defcoll.coll
            ELSE c.collname
       END AS collation
FROM pg_index AS i
   CROSS JOIN unnest(i.indcollation) WITH ORDINALITY AS icol(coll, pos)
   CROSS JOIN defcoll
   LEFT JOIN pg_collation AS c ON c.oid = icol.coll
WHERE i.indexrelid = 'idx_test'::regclass
ORDER BY icol.pos;

 pos | collation 
-----+-----------
   1 | C
(1 row)

Postgresql 数据库级别、table 级别、列级别的排序规则

Collation in Postgresql DB level,table level, column level

postgresql

collation