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

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)

其他回答

如果你想保持索引中的列顺序,这里有一个(非常丑陋的)方法:

select table_name,
    index_name,
    array_agg(column_name)
from (
    select
        t.relname as table_name,
        i.relname as index_name,
        a.attname as column_name,
        unnest(ix.indkey) as unn,
        a.attnum
    from
        pg_class t,
        pg_class i,
        pg_index ix,
        pg_attribute a
    where
        t.oid = ix.indrelid
        and i.oid = ix.indexrelid
        and a.attrelid = t.oid
        and a.attnum = ANY(ix.indkey)
        and t.relkind = 'r'
        and t.relnamespace = <oid of the schema you're interested in>
    order by
        t.relname,
        i.relname,
        generate_subscripts(ix.indkey,1)) sb
where unn = attnum
group by table_name, index_name

列顺序存储在pg_index中。indkey列,我是根据这个数组的下标排序的。

结合其他代码并创建一个视图:

CREATE OR REPLACE VIEW view_index AS 
SELECT
     n.nspname  as "schema"
    ,t.relname  as "table"
    ,c.relname  as "index"
    ,pg_get_indexdef(indexrelid) as "def"
FROM pg_catalog.pg_class c
    JOIN pg_catalog.pg_namespace n ON n.oid        = c.relnamespace
    JOIN pg_catalog.pg_index i ON i.indexrelid = c.oid
    JOIN pg_catalog.pg_class t ON i.indrelid   = t.oid
WHERE c.relkind = 'i'
    and n.nspname not in ('pg_catalog', 'pg_toast')
    and pg_catalog.pg_table_is_visible(c.oid)
ORDER BY
     n.nspname
    ,t.relname
    ,c.relname;

类似于接受的答案,但有左连接pg_attribute作为正常连接或查询pg_attribute不给出索引,如: 为用户创建唯一索引unique_user_name_index (lower(name))

select 
    row_number() over (order by c.relname),
    c.relname as index, 
    t.relname as table, 
    array_to_string(array_agg(a.attname), ', ') as column_names 
from pg_class c
join pg_index i on c.oid = i.indexrelid and c.relkind='i' and c.relname not like 'pg_%' 
join pg_class t on t.oid = i.indrelid
left join pg_attribute a on a.attrelid = t.oid and a.attnum = ANY(i.indkey) 
group by t.relname, c.relname order by c.relname;

原始信息在pg_index中。

我认为这个版本在这个线程上还不存在:它提供了列名列表和索引的ddl。

CREATE OR REPLACE VIEW V_TABLE_INDEXES AS

SELECT
     n.nspname  as "schema"
    ,t.relname  as "table"
    ,c.relname  as "index"
    ,i.indisunique AS "is_unique"
    ,array_to_string(array_agg(a.attname), ', ') as "columns"
    ,pg_get_indexdef(i.indexrelid) as "ddl"
FROM pg_catalog.pg_class c
    JOIN pg_catalog.pg_namespace n ON n.oid        = c.relnamespace
    JOIN pg_catalog.pg_index i ON i.indexrelid = c.oid
    JOIN pg_catalog.pg_class t ON i.indrelid   = t.oid
    JOIN pg_attribute a ON a.attrelid = t.oid AND a.attnum = ANY(i.indkey)
WHERE c.relkind = 'i'
      and n.nspname not in ('pg_catalog', 'pg_toast')
      and pg_catalog.pg_table_is_visible(c.oid)
GROUP BY
    n.nspname
    ,t.relname
    ,c.relname
    ,i.indisunique
    ,i.indexrelid
ORDER BY
    n.nspname
    ,t.relname
    ,c.relname;

我发现使用函数的索引不链接到列名,所以偶尔你会发现一个索引列表,例如一个列名,而实际上是使用3。

例子:

CREATE INDEX ui1 ON table1 (coalesce(col1,''),coalesce(col2,''),col3)

该查询仅返回'col3'作为索引上的列,但DDL显示了索引中使用的全部列。