PSQL:如何优化此查询的执行时间
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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
这里是限制为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
这里是无限制的说明:
-> 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,如果::“ factures”和“ echeances”表具有大量行,
在子查询中指定了限制,例如限制为100000,查询时间很快
Limit在子查询中未指定,这需要很多时间,我不得不在等待15分钟以上后将其停止。
目标是使此查询不受限制并在合理的时间内运行。
我有以下查询:从“ factures”中选择SELECT“ factures”。“ id”(“ factures”。“ id” NOT IN(从“ echeances”中选择DISTINCT(“ echeances”。“ facture_id”)...
答案
切换到NOT EXISTS
:
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