DELETE with NOT IN (SELECT ...) 的性能
Performance of DELETE with NOT IN (SELECT ...)
我有这两个表,想从 ms_author 中删除作者中不存在的所有作者。
author
(160 万行)
+-------+-------------+------+-----+-------+
| Field | Type | Null | Key | index |
+-------+-------------+------+-----+-------+
| id | text | NO | PRI | true |
| name | text | YES | | |
+-------+-------------+------+-----+-------+
ms_author
(1.2 亿行)
+-------+-------------+------+-----+-------+
| Field | Type | Null | Key | index |
+-------+-------------+------+-----+-------+
| id | text | NO | PRI | |
| name | text | YES | | true |
+-------+-------------+------+-----+-------+
这是我的查询:
DELETE
FROM ms_author AS m
WHERE m.name NOT IN
(SELECT a.name
FROM author AS a);
我试着估计查询持续时间:~ 130 小时。
有没有更快的方法来实现这个目标?
编辑:
EXPLAIN VERBOSE
输出
Delete on public.ms_author m (cost=0.00..2906498718724.75 rows=59946100 width=6)"
-> Seq Scan on public.ms_author m (cost=0.00..2906498718724.75 rows=59946100 width=6)"
Output: m.ctid"
Filter: (NOT (SubPlan 1))"
SubPlan 1"
-> Materialize (cost=0.00..44334.43 rows=1660295 width=15)"
Output: a.name"
-> Seq Scan on public.author a (cost=0.00..27925.95 rows=1660295 width=15)"
Output: a.name"
索引作者(name
):
create index author_name on author(name);
索引 ms_author(名称):
create index ms_author_name on ms_author(name);
您使用 NOT IN
的删除查询通常会导致嵌套循环反连接,从而导致性能不佳。您可以按如下方式重写您的查询:
你可以这样写:
DELETE FROM ms_author AS m
WHERE m.id IN
(SELECT m.id FROM ms_author AS m
LEFT JOIN author AS a ON m.name = a.name
WHERE a.name IS NULL);
这种方法还有一个额外的优势,那就是您使用主键 'id' 来删除行,这应该快得多。
我是 "anti-join." 的忠实粉丝 这对大型和小型数据集都有效:
delete from ms_author ma
where not exists (
select null
from author a
where ma.name = a.name
)
我有这两个表,想从 ms_author 中删除作者中不存在的所有作者。
author
(160 万行)
+-------+-------------+------+-----+-------+
| Field | Type | Null | Key | index |
+-------+-------------+------+-----+-------+
| id | text | NO | PRI | true |
| name | text | YES | | |
+-------+-------------+------+-----+-------+
ms_author
(1.2 亿行)
+-------+-------------+------+-----+-------+
| Field | Type | Null | Key | index |
+-------+-------------+------+-----+-------+
| id | text | NO | PRI | |
| name | text | YES | | true |
+-------+-------------+------+-----+-------+
这是我的查询:
DELETE
FROM ms_author AS m
WHERE m.name NOT IN
(SELECT a.name
FROM author AS a);
我试着估计查询持续时间:~ 130 小时。
有没有更快的方法来实现这个目标?
编辑:
EXPLAIN VERBOSE
输出
Delete on public.ms_author m (cost=0.00..2906498718724.75 rows=59946100 width=6)"
-> Seq Scan on public.ms_author m (cost=0.00..2906498718724.75 rows=59946100 width=6)"
Output: m.ctid"
Filter: (NOT (SubPlan 1))"
SubPlan 1"
-> Materialize (cost=0.00..44334.43 rows=1660295 width=15)"
Output: a.name"
-> Seq Scan on public.author a (cost=0.00..27925.95 rows=1660295 width=15)"
Output: a.name"
索引作者(name
):
create index author_name on author(name);
索引 ms_author(名称):
create index ms_author_name on ms_author(name);
您使用 NOT IN
的删除查询通常会导致嵌套循环反连接,从而导致性能不佳。您可以按如下方式重写您的查询:
你可以这样写:
DELETE FROM ms_author AS m
WHERE m.id IN
(SELECT m.id FROM ms_author AS m
LEFT JOIN author AS a ON m.name = a.name
WHERE a.name IS NULL);
这种方法还有一个额外的优势,那就是您使用主键 'id' 来删除行,这应该快得多。
我是 "anti-join." 的忠实粉丝 这对大型和小型数据集都有效:
delete from ms_author ma
where not exists (
select null
from author a
where ma.name = a.name
)