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

PostgreSQL (pg_indexes):

SELECT * FROM pg_indexes WHERE tablename = 'mytable';

MySQL(显示索引)

SHOW INDEX FROM mytable;

其他回答

原始信息在pg_index中。

下面是一个包装cope360答案的函数:

CREATE OR REPLACE FUNCTION getIndices(_table_name varchar)
  RETURNS TABLE(table_name varchar, index_name varchar, column_name varchar) AS $$
  BEGIN
    RETURN QUERY
    select
    t.relname::varchar as table_name,
    i.relname::varchar as index_name,
    a.attname::varchar as column_name
from
    pg_class t,
    pg_class i,
    pg_index ix,
    pg_attribute a
where
    t.oid = ix.indrelid
    and i.oid = ix.indexrelid
    and a.attrelid = t.oid
    and a.attnum = ANY(ix.indkey)
    and t.relkind = 'r'
    and t.relname = _table_name
order by
    t.relname,
    i.relname;
  END;
  $$ LANGUAGE plpgsql;

用法:

select * from getIndices('<my_table>')

@cope360接受的答案很好,但我想要一些更像Oracle的DBA_IND_COLUMNS, ALL_IND_COLUMNS和USER_IND_COLUMNS(例如,报告表/索引模式和索引在多列索引中的位置),所以我把接受的答案改编成这样:

with
 ind_cols as (
select
    n.nspname as schema_name,
    t.relname as table_name,
    i.relname as index_name,
    a.attname as column_name,
    1 + array_position(ix.indkey, a.attnum) as column_position
from
     pg_catalog.pg_class t
join pg_catalog.pg_attribute a on t.oid    =      a.attrelid 
join pg_catalog.pg_index ix    on t.oid    =     ix.indrelid
join pg_catalog.pg_class i     on a.attnum = any(ix.indkey)
                              and i.oid    =     ix.indexrelid
join pg_catalog.pg_namespace n on n.oid    =      t.relnamespace
where t.relkind = 'r'
order by
    t.relname,
    i.relname,
    array_position(ix.indkey, a.attnum)
)
select * 
from ind_cols
where schema_name = 'test'
  and table_name  = 'indextest'
order by schema_name, table_name
;

这将给出如下输出:

 schema_name | table_name | index_name | column_name | column_position 
-------------+------------+------------+-------------+-----------------
 test        | indextest  | testind1   | singleindex |               1
 test        | indextest  | testind2   | firstoftwo  |               1
 test        | indextest  | testind2   | secondoftwo |               2
(3 rows)

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。

# \迪

最简单和最短的方法是\di,它将列出当前数据库中的所有索引。

$ \di
                      List of relations
 Schema |            Name             | Type  |  Owner   |     Table     
--------+-----------------------------+-------+----------+---------------
 public | part_delivery_index         | index | shipper  | part_delivery
 public | part_delivery_pkey          | index | shipper  | part_delivery
 public | shipment_by_mandator        | index | shipper  | shipment_info
 public | shipment_by_number_and_size | index | shipper  | shipment_info
 public | shipment_info_pkey          | index | shipper  | shipment_info
(5 rows)

\di是\d命令的“小兄弟”,该命令将列出当前数据库的所有关系。因此\di当然代表“显示我这个数据库索引”。

输入\diS将列出系统范围内使用的所有索引,这意味着您也将获得所有pg_catalog索引。

$ \diS
                                      List of relations
   Schema   |                   Name                    | Type  |  Owner   |          Table
------------+-------------------------------------------+-------+----------+-------------------------
 pg_catalog | pg_aggregate_fnoid_index                  | index | postgres | pg_aggregate
 pg_catalog | pg_am_name_index                          | index | postgres | pg_am
 pg_catalog | pg_am_oid_index                           | index | postgres | pg_am
 pg_catalog | pg_amop_fam_strat_index                   | index | postgres | pg_amop
 pg_catalog | pg_amop_oid_index                         | index | postgres | pg_amop
 pg_catalog | pg_amop_opr_fam_index                     | index | postgres | pg_amop
 pg_catalog | pg_amproc_fam_proc_index                  | index | postgres | pg_amproc
 pg_catalog | pg_amproc_oid_index                       | index | postgres | pg_amproc
 pg_catalog | pg_attrdef_adrelid_adnum_index            | index | postgres | pg_attrdef
--More-- 

使用这两个命令,您可以在它之后添加一个+,以获得更多信息,如大小-磁盘空间-索引需要和描述(如果可用)。

$ \di+
                                 List of relations
 Schema |            Name             | Type  |  Owner   |     Table     | Size  | Description 
--------+-----------------------------+-------+----------+---------------+-------+-------------
 public | part_delivery_index         | index | shipper  | part_delivery | 16 kB | 
 public | part_delivery_pkey          | index | shipper  | part_delivery | 16 kB | 
 public | shipment_by_mandator        | index | shipper  | shipment_info | 19 MB | 
 public | shipment_by_number_and_size | index | shipper  | shipment_info | 19 MB | 
 public | shipment_info_pkey          | index | shipper  | shipment_info | 53 MB | 
(5 rows)

在psql中,你可以很容易地找到关于输入\?