我想在PostgreSQL中获得索引上的列。

在MySQL中,您可以使用SHOW INDEXES FOR表并查看Column_name列。

mysql> show indexes from foos;

+-------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name            | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| foos  |          0 | PRIMARY             |            1 | id          | A         |       19710 |     NULL | NULL   |      | BTREE      |         | 
| foos  |          0 | index_foos_on_email |            1 | email       | A         |       19710 |     NULL | NULL   | YES  | BTREE      |         | 
| foos  |          1 | index_foos_on_name  |            1 | name        | A         |       19710 |     NULL | NULL   |      | BTREE      |         | 
+-------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+

PostgreSQL中存在类似的东西吗?

我已经在psql命令提示符中尝试了\d(使用-E选项来显示SQL),但它没有显示我正在寻找的信息。

更新:感谢大家的回答。cope360提供了我想要的东西,但也有一些人提供了非常有用的链接。为了将来的参考,请查看pg_index的文档(通过Milen A. Radev)和非常有用的文章从PostgreSQL提取META信息(通过micharov Niklas)。


当前回答

查询结果:

table |     column     |          type          | notnull |  index_name  | is_index | primarykey | uniquekey | default
-------+----------------+------------------------+---------+--------------+----------+-   -----------+-----------+---------
 nodes | dns_datacenter | character varying(255) | f       |              | f        | f          | f         |
 nodes | dns_name       | character varying(255) | f       | dns_name_idx | t        | f          | f         |
 nodes | id             | uuid                   | t       | nodes_pkey   | t        | t          | t         |
(3 rows)

查询:

SELECT  
c.relname AS table,
f.attname AS column,  
pg_catalog.format_type(f.atttypid,f.atttypmod) AS type,
f.attnotnull AS notnull,  
i.relname as index_name,
CASE  
    WHEN i.oid<>0 THEN 't'  
    ELSE 'f'  
END AS is_index,  
CASE  
    WHEN p.contype = 'p' THEN 't'  
    ELSE 'f'  
END AS primarykey,  
CASE  
    WHEN p.contype = 'u' THEN 't' 
    WHEN p.contype = 'p' THEN 't' 
    ELSE 'f'
END AS uniquekey,
CASE
    WHEN f.atthasdef = 't' THEN d.adsrc
END AS default  FROM pg_attribute f  
JOIN pg_class c ON c.oid = f.attrelid  
JOIN pg_type t ON t.oid = f.atttypid  
LEFT JOIN pg_attrdef d ON d.adrelid = c.oid AND d.adnum = f.attnum  
LEFT JOIN pg_namespace n ON n.oid = c.relnamespace  
LEFT JOIN pg_constraint p ON p.conrelid = c.oid AND f.attnum = ANY (p.conkey)  
LEFT JOIN pg_class AS g ON p.confrelid = g.oid
LEFT JOIN pg_index AS ix ON f.attnum = ANY(ix.indkey) and c.oid = f.attrelid and c.oid = ix.indrelid 
LEFT JOIN pg_class AS i ON ix.indexrelid = i.oid 

WHERE c.relkind = 'r'::char  
AND n.nspname = 'public'  -- Replace with Schema name 
--AND c.relname = 'nodes'  -- Replace with table name, or Comment this for get all tables
AND f.attnum > 0
ORDER BY c.relname,f.attname;

其他回答

@cope360的精彩回答,转换为使用连接语法。

select t.relname as table_name
     , i.relname as index_name
     , array_to_string(array_agg(a.attname), ', ') as column_names
from pg_class t
join pg_index ix
on t.oid = ix.indrelid
join pg_class i
on i.oid = ix.indexrelid
join pg_attribute a
on a.attrelid = t.oid
and a.attnum = ANY(ix.indkey)
where t.relkind = 'r'
and t.relname like 'test%'
group by t.relname
       , i.relname
order by t.relname
       , i.relname
;
select t.relname as table_name, 
       i.relname as index_name, 
       array_position(ix.indkey,a.attnum) pos, 
       a.attname as column_name
from pg_class t
join pg_index ix on t.oid = ix.indrelid
join pg_class i on i.oid = ix.indexrelid
join pg_attribute a on a.attrelid = t.oid and a.attnum = ANY(ix.indkey)
where t.relkind = 'r'
and t.relname like 'orders'
order by t.relname, i.relname, array_position(ix.indkey,a.attnum)

原始信息在pg_index中。

只需要执行:\d table_name

但是我不确定你说没有列的信息是什么意思。

例如:

# \d pg_class
       Table "pg_catalog.pg_class"
     Column      |   Type    | Modifiers
-----------------+-----------+-----------
 relname         | name      | not null
 relnamespace    | oid       | not null
 reltype         | oid       | not null
 reloftype       | oid       | not null
 relowner        | oid       | not null
 relam           | oid       | not null
 relfilenode     | oid       | not null
 reltablespace   | oid       | not null
 relpages        | integer   | not null
 reltuples       | real      | not null
 reltoastrelid   | oid       | not null
 reltoastidxid   | oid       | not null
 relhasindex     | boolean   | not null
 relisshared     | boolean   | not null
 relistemp       | boolean   | not null
 relkind         | "char"    | not null
 relnatts        | smallint  | not null
 relchecks       | smallint  | not null
 relhasoids      | boolean   | not null
 relhaspkey      | boolean   | not null
 relhasexclusion | boolean   | not null
 relhasrules     | boolean   | not null
 relhastriggers  | boolean   | not null
 relhassubclass  | boolean   | not null
 relfrozenxid    | xid       | not null
 relacl          | aclitem[] |
 reloptions      | text[]    |
Indexes:
    "pg_class_oid_index" UNIQUE, btree (oid)
    "pg_class_relname_nsp_index" UNIQUE, btree (relname, relnamespace)

它清楚地显示给定索引在该表上的列。

稍微修改一下@cope360的回答:

create table test (a int, b int, c int, constraint pk_test primary key(c, a, b));
select i.relname as index_name,
       ix.indisunique as is_unique,
       a.attname as column_name,
from pg_class c
       inner join pg_index ix on c.oid=ix.indrelid
       inner join pg_class i on ix.indexrelid=i.oid
       inner join pg_attribute a on a.attrelid=c.oid and a.attnum=any(ix.indkey)
where c.oid='public.test'::regclass::oid
order by array_position(ix.indkey, a.attnum) asc;

这将显示索引列的正确顺序:

index_name      is_unique  column_name
pk_test         true       c
pk_test         true       a
pk_test         true       b