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我有以下查询：

SELECT "factures"."id" 
FROM   "factures" 
WHERE  ( "factures"."id" NOT IN (SELECT DISTINCT( "echeances"."facture_id" ) 
                                 FROM   "echeances" 
                                 WHERE  "echeances"."type_decheance" IN ( 2, 3, 4, 5, 8, 9 ) 
                                        AND "echeances"."facture_id" IS NOT NULL 
                                 LIMIT  100000)) <----- removing this limit makes the query take enormous time
ORDER  BY "factures"."id" DESC

这是限制为 100 000 的解释分析：

Index Only Scan Backward using factures_id_pkey on factures  (cost=93516.76..211292.17 rows=530570 width=4) (actual time=1425.701..11466.759 rows=963698 loops=1)
  Filter: (NOT (hashed SubPlan 1))
  Rows Removed by Filter: 99997
  Heap Fetches: 1063695
  SubPlan 1
    ->  Limit  (cost=0.43..93266.34 rows=100000 width=4) (actual time=0.022..1229.925 rows=100000 loops=1)
          ->  Unique  (cost=0.43..264837.37 rows=283959 width=4) (actual time=0.022..1090.692 rows=100000 loops=1)
                ->  Index Scan using echeances__facture_id__idx on echeances  (cost=0.43..262883.29 rows=781631 width=4) (actual time=0.020..819.735 rows=100167 loops=1)
                      Index Cond: (facture_id IS NOT NULL)
"                      Filter: (type_decheance = ANY ('{2,3,4,5,8,9}'::integer[]))"
                      Rows Removed by Filter: 156995
Planning time: 0.249 ms
Execution time: 11960.423 ms

以下是无限制的解释：

->  Unique  (cost=0.43..264837.37 rows=283959 width=4)
Index Only Scan Backward using factures_id_pkey on factures  (cost=0.86..142233669403.15 rows=530570 width=4)
  Filter: (NOT (SubPlan 1))
  SubPlan 1
    ->  Materialize  (cost=0.43..267367.16 rows=283959 width=4)
                ->  Index Scan using echeances__facture_id__idx on echeances  (cost=0.43..262883.29 rows=781631 width=4)
                      Index Cond: (facture_id IS NOT NULL)
"                      Filter: (type_decheance = ANY ('{2,3,4,5,8,9}'::integer[]))"

这是架构

Table "factures"
id

Table "echeances"
id
facture_id (fk)
type_decheance (integer)

问题是“factures”和“echeances”表有大量的行，如果：

  • 在子查询中指定limit，例如limit 100000，查询时间快

  • 子查询中没有指定limit，需要很多时间，我等了15多分钟后才停止。

目标是让这个查询在合理的时间内不受限制地运行。

4

1 回答 1

2

切换到NOT EXISTS：

SELECT f.id
FROM factures f
WHERE NOT EXISTS (SELECT 1
                  FROM echeances e
                  WHERE e.facture_id = f.id AND
                        e.type_decheance IN ( 2, 3, 4, 5, 8, 9 ) 
                 )
ORDER  BY f.id DESC;

请注意，我删除了所有双引号。不要引用您的标识符。它只是使查询更难编写和阅读。

然后你想要一个关于echeances(facture_id, type_decheance). 这应该很快，因为可以通过简单的索引查找来检查每个facture id。

于 2020-05-21T19:16:36.070 回答