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)
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;
在处理索引时，索引中构造列的顺序与列本身同样重要。
下面的查询以排序的方式列出给定表的所有索引及其所有列。
SELECT
table_name,
index_name,
string_agg(column_name, ',')
FROM (
SELECT
t.relname AS table_name,
i.relname AS index_name,
a.attname AS column_name,
(SELECT i
FROM (SELECT
*,
row_number()
OVER () i
FROM unnest(indkey) WITH ORDINALITY AS a(v)) a
WHERE v = 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.relname LIKE 'tablename'
ORDER BY table_name, index_name, i
) raw
GROUP BY table_name, index_name
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>')
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。
