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)。
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
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)
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)
延伸到@Cope360的好答案。要获取某个表(如果它们是相同的表名但不同的模式)，只需使用表OID。
select
t.relname as table_name
,i.relname as index_name
,a.attname as column_name
,a.attrelid tableid
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 like 'tbassettype'
and a.attrelid = '"dbLegal".tbassettype'::regclass
order by
t.relname,
i.relname;
解释:我有表名'tbassettype'在两个模式'dbAsset'和'dbLegal'。要在dbLegal上只获取表，只需让a.attrelid =它的OID。
