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)。
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。
# \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\?
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。
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)
一些样本数据…
create table test (a int, b int, c int, constraint pk_test primary key(a, b));
create table test2 (a int, b int, c int, constraint uk_test2 unique (b, c));
create table test3 (a int, b int, c int, constraint uk_test3b unique (b), constraint uk_test3c unique (c), constraint uk_test3ab unique (a, b));
使用pg_get_indexdef函数:
select pg_get_indexdef(indexrelid) from pg_index where indrelid = 'test'::regclass;
pg_get_indexdef
--------------------------------------------------------
CREATE UNIQUE INDEX pk_test ON test USING btree (a, b)
(1 row)
select pg_get_indexdef(indexrelid) from pg_index where indrelid = 'test2'::regclass;
pg_get_indexdef
----------------------------------------------------------
CREATE UNIQUE INDEX uk_test2 ON test2 USING btree (b, c)
(1 row)
select pg_get_indexdef(indexrelid) from pg_index where indrelid ='test3'::regclass;
pg_get_indexdef
------------------------------------------------------------
CREATE UNIQUE INDEX uk_test3b ON test3 USING btree (b)
CREATE UNIQUE INDEX uk_test3c ON test3 USING btree (c)
CREATE UNIQUE INDEX uk_test3ab ON test3 USING btree (a, b)
(3 rows)
