저는 postgres v9.6.5를 사용하고 있습니다. 복잡한 쿼리를 사용하지 않고 왜 느려지는지 궁금해하고 있습니다. (실제로 느리지 만 실제로는 수천 행과 같은 많은 데이터가 없습니다.) 여기 포스트그레스 쿼리를 설명하십시오. 왜 훨씬 더 길고 WHERE 및 LIMIT를 사용하는 쿼리입니까
쿼리입니다 :SELECT o0.*
FROM "orders" AS o0
JOIN "balances" AS b1 ON b1."id" = o0."balance_id"
JOIN "users" AS u3 ON u3."id" = b1."user_id"
WHERE (u3."partner_id" = 3)
ORDER BY o0."id" DESC LIMIT 10;
그리고 그 쿼리 계획이다 :
Limit (cost=0.43..12.84 rows=10 width=148) (actual time=0.062..53.866 rows=4 loops=1)
-> Nested Loop (cost=0.43..4750.03 rows=3826 width=148) (actual time=0.061..53.864 rows=4 loops=1)
Join Filter: (b1.user_id = u3.id)
Rows Removed by Join Filter: 67404
-> Nested Loop (cost=0.43..3945.32 rows=17856 width=152) (actual time=0.025..38.457 rows=16852 loops=1)
-> Index Scan Backward using orders_pkey on orders o0 (cost=0.29..897.80 rows=17856 width=148) (actual time=0.016..11.558 rows=16852 loops=1)
-> Index Scan using balances_pkey on balances b1 (cost=0.14..0.16 rows=1 width=8) (actual time=0.001..0.001 rows=1 loops=16852)
Index Cond: (id = o0.balance_id)
-> Materialize (cost=0.00..1.19 rows=3 width=4) (actual time=0.000..0.000 rows=4 loops=16852)
-> Seq Scan on users u3 (cost=0.00..1.18 rows=3 width=4) (actual time=0.023..0.030 rows=4 loops=1)
Filter: (partner_id = 3)
Rows Removed by Filter: 12
Planning time: 0.780 ms
Execution time: 54.053 ms
실제로 LIMIT
없이 노력하고 내가 상당히 다른 계획을 가지고 : 또한
Sort (cost=874.23..883.80 rows=3826 width=148) (actual time=11.361..11.362 rows=4 loops=1)
Sort Key: o0.id DESC
Sort Method: quicksort Memory: 26kB
-> Hash Join (cost=3.77..646.55 rows=3826 width=148) (actual time=11.300..11.346 rows=4 loops=1)
Hash Cond: (o0.balance_id = b1.id)
-> Seq Scan on orders o0 (cost=0.00..537.56 rows=17856 width=148) (actual time=0.012..8.464 rows=16852 loops=1)
-> Hash (cost=3.55..3.55 rows=18 width=4) (actual time=0.125..0.125 rows=24 loops=1)
Buckets: 1024 Batches: 1 Memory Usage: 9kB
-> Hash Join (cost=1.21..3.55 rows=18 width=4) (actual time=0.046..0.089 rows=24 loops=1)
Hash Cond: (b1.user_id = u3.id)
-> Seq Scan on balances b1 (cost=0.00..1.84 rows=84 width=8) (actual time=0.011..0.029 rows=96 loops=1)
-> Hash (cost=1.18..1.18 rows=3 width=4) (actual time=0.028..0.028 rows=4 loops=1)
Buckets: 1024 Batches: 1 Memory Usage: 9kB
-> Seq Scan on users u3 (cost=0.00..1.18 rows=3 width=4) (actual time=0.014..0.021 rows=4 loops=1)
Filter: (partner_id = 3)
Rows Removed by Filter: 12
Planning time: 0.569 ms
Execution time: 11.420 ms
그리고없이를 WHERE
(단 LIMIT
) :
Limit (cost=0.43..4.74 rows=10 width=148) (actual time=0.023..0.066 rows=10 loops=1)
-> Nested Loop (cost=0.43..7696.26 rows=17856 width=148) (actual time=0.022..0.065 rows=10 loops=1)
Join Filter: (b1.user_id = u3.id)
Rows Removed by Join Filter: 139
-> Nested Loop (cost=0.43..3945.32 rows=17856 width=152) (actual time=0.009..0.029 rows=10 loops=1)
-> Index Scan Backward using orders_pkey on orders o0 (cost=0.29..897.80 rows=17856 width=148) (actual time=0.007..0.015 rows=10 loops=1)
-> Index Scan using balances_pkey on balances b1 (cost=0.14..0.16 rows=1 width=8) (actual time=0.001..0.001 rows=1 loops=10)
Index Cond: (id = o0.balance_id)
-> Materialize (cost=0.00..1.21 rows=14 width=4) (actual time=0.001..0.001 rows=15 loops=10)
-> Seq Scan on users u3 (cost=0.00..1.14 rows=14 width=4) (actual time=0.005..0.007 rows=16 loops=1)
Planning time: 0.286 ms
Execution time: 0.097 ms
WHERE
이 없으면 훨씬 빠릅니다. 누군가가 나를 더 잘 이해할 수있는 계획에 대한 설명을 어디서 찾을 수 있습니까? 또한 이러한 쿼리를 더 빨리 수행하기 위해 무엇을 할 수 있습니까? 아니면 100 배나 더 많은 데이터를 가지고도 충분히 빠를 것입니다 .- 내게 50ms가 적당합니다. tb30)
감사합니다. –