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)。
@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
;
# \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\?
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
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)
