小编ciz*_*zer的帖子

我有一个DELETE查询,我需要在PostgreSQL 9.0.4上运行.我发现它是高性能的,直到它在subselect查询中遇到524,289行.

例如,在524,288,没有使用物化视图,成本看起来很不错:

explain DELETE FROM table1 WHERE pointLevel = 0 AND userID NOT IN
(SELECT userID FROM table2 fetch first 524288 rows only);
                                                QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Delete  (cost=13549.49..17840.67 rows=21 width=6)
   ->  Index Scan using jslps_userid_nopt on table1  (cost=13549.49..17840.67 rows=21 width=6)
         Filter: ((NOT (hashed SubPlan 1)) AND (pointlevel = 0))
         SubPlan 1
           ->  Limit  (cost=0.00..12238.77 rows=524288 width=8)
                 ->  Seq Scan on table2  (cost=0.00..17677.92 rows=757292 width=8)
(6 rows)

但是,一旦我达到524,289,物化视图就会发挥作用,DELETE查询变得更加昂贵:

explain DELETE FROM table1 WHERE pointLevel = 0 AND userID NOT IN …