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)。
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;
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)
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
请尝试下面的查询以深入到所需的索引
查询如下-我亲自尝试过，并经常使用它。
SELECT n.nspname as "Schema",
c.relname as "Name",
CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'i'
THEN 'index' WHEN 'S' THEN 'sequence' WHEN 's' THEN 'special' END as "Type",
u.usename as "Owner",
c2.relname as "Table"
FROM pg_catalog.pg_class c
JOIN pg_catalog.pg_index i ON i.indexrelid = c.oid
JOIN pg_catalog.pg_class c2 ON i.indrelid = c2.oid
LEFT JOIN pg_catalog.pg_user u ON u.usesysid = c.relowner
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('i','')
AND n.nspname NOT IN ('pg_catalog', 'pg_toast')
AND pg_catalog.pg_table_is_visible(c.oid)
AND c2.relname like '%agg_transaction%' --table name
AND nspname = 'edjus' -- schema name
ORDER BY 1,2;
