sql查詢慢3 leftjoins與其中clausel

Question

這第一個查詢有一個和clausle更多，從200毫秒減慢到9-13秒 我不明白爲什麼它如此。

如果我刪除所有where子句我得到〜200ms只是如果我再添加一個，它會很慢。

SELECT DISTINCT a.* , p.*, p2.*, p3.* 
FROM article a 
LEFT JOIN pro p ON a.id = p.article_id 
LEFT JOIN pro p2 ON a.id = p2.article_id 
LEFT JOIN pro p3 ON a.id = p3.article_id 
WHERE a.is_active = true 
AND p.name = 'hotel_stars' 
AND p2.name = 'article_journey_days' 
AND p3.name = 'article_persons' 
AND p3.int_value > 0 AND p3.int_value < 7 
AND p.int_value > 0 AND p.int_value < 5 

結果

319 Datensätze 

Laufzeit gesamt: 9,602.081 ms 

SELECT DISTINCT a.* , p.*, p2.*, p3.* 
FROM article a 
LEFT JOIN property p ON a.id = p.article_id 
LEFT JOIN property p2 ON a.id = p2.article_id 
LEFT JOIN property p3 ON a.id = p3.article_id 
WHERE a.is_active = true 
AND p.name = 'hotel_stars' 
AND p2.name = 'article_property_journey_days' 
AND p3.name = 'article_property_persons' 
AND p3.int_value > 0 AND p3.int_value < 7 
// AND p.int_value > 0 AND p.int_value < 5 (removed) 

結果

469 Datensätze 

Laufzeit gesamt: 278.453 ms 

問題出在哪裏？ THX

編輯EXPLAIN PLAN：

HashAggregate (cost=24113.80..24113.81 rows=1 width=3528) 
    -> Nested Loop (cost=0.00..24113.69 rows=1 width=3528) 
     Join Filter: (a.id = p2.article_id) 
     -> Nested Loop (cost=0.00..16889.70 rows=1 width=2488) 
       -> Nested Loop (cost=0.00..16856.58 rows=4 width=2080) 
        Join Filter: (p.article_id = p3.article_id) 
        -> Seq Scan on property p (cost=0.00..8335.87 rows=115 width=1040) 
          Filter: ((int_value > 0) AND (int_value < 5) AND ((name)::text = 'hotel_stars'::text)) 
        -> Materialize (cost=0.00..8336.41 rows=107 width=1040) 
          -> Seq Scan on property p3 (cost=0.00..8335.87 rows=107 width=1040) 
           Filter: ((int_value > 0) AND (int_value < 7) AND ((name)::text = 'article_property_persons'::text)) 
       -> Index Scan using article_pkey on article a (cost=0.00..8.27 rows=1 width=408) 
        Index Cond: (id = p.article_id) 
        Filter: is_active 
     -> Seq Scan on property p2 (cost=0.00..7185.05 rows=3115 width=1040) 
       Filter: ((name)::text = 'article_property_journey_days'::text) 
16 Datensätze 

Laufzeit gesamt: 11.153 ms 

改爲

SELECT DISTINCT a.* , p.*, p2.*, p3.* 
    FROM article a 
    INNER JOIN pro p ON a.id = p.article_id AND p.name = 'hotel_stars' AND p.int_value > 0 AND p.int_value < 5 
    INNER JOIN pro p2 ON a.id = p2.article_id AND p2.name = 'article_journey_days' 
    INNER JOIN pro p3 ON a.id = p3.article_id AND p3.name = 'article_persons' AND p3.int_value > 0 AND p3.int_value < 7 
    WHERE a.is_active = true 

結果：

319 Datensätze 

Laufzeit gesamt: 9,315.863 ms 

HashAggregate (cost=24113.80..24113.81 rows=1 width=3528) 
    -> Nested Loop (cost=0.00..24113.69 rows=1 width=3528) 
     Join Filter: (a.id = p2.article_id) 
     -> Nested Loop (cost=0.00..16889.70 rows=1 width=2488) 
       -> Nested Loop (cost=0.00..16856.58 rows=4 width=2080) 
        Join Filter: (p.article_id = p3.article_id) 
        -> Seq Scan on property p (cost=0.00..8335.87 rows=115 width=1040) 
          Filter: ((int_value > 0) AND (int_value < 5) AND ((name)::text = 'hotel_stars'::text)) 
        -> Materialize (cost=0.00..8336.41 rows=107 width=1040) 
          -> Seq Scan on property p3 (cost=0.00..8335.87 rows=107 width=1040) 
           Filter: ((int_value > 0) AND (int_value < 7) AND ((name)::text = 'article_property_persons'::text)) 
       -> Index Scan using article_pkey on article a (cost=0.00..8.27 rows=1 width=408) 
        Index Cond: (id = p.article_id) 
        Filter: is_active 
     -> Seq Scan on property p2 (cost=0.00..7185.05 rows=3115 width=1040) 
       Filter: ((name)::text = 'article_property_journey_days'::text) 
16 Datensätze 

Laufzeit gesamt: 4.314 ms 

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Answer 1

新增指數科拉姆n p.name和p.article。 結果速度從13秒提高到180毫秒。