在同一张表上使用许多内连接优化 SQL 查询

Question

我遇到了性能问题：

一家商店有一个商品过滤器，其中包含“颜色”、“尺寸”、“性别”和“特征”类别。所有这些详细信息都存储在article_criterias 表中，如下所示：

article_criterias的表格布局是；该表大约有 36.000 行：

article_id | group    | option | option_val
       100 | "size"   | "35"   |     35.00
       100 | "size"   | "36"   |     36.00
       100 | "size"   | "36½"  |     36.50
       100 | "color"  | "40"   |     40.00
       100 | "color"  | "50"   |     50.00
       100 | "gender" | "1"    |      1.00
       101 | "size"   | "40"   |     40.00
       ...

我们有一个根据当前选择的条件动态构建的 SQL 查询。该查询适用于 2-3 个条件，但在选择超过 5 个选项时会变得非常慢（每个额外的 INNER JOIN 大约会使执行时间增加一倍）

我们怎样才能让这个 SQL 更快，甚至可以用更高效的概念代替内部连接？

这是查询（逻辑正确，只是性能不好）：

-- This SQL is generated when the user selected the following criteria
-- gender: 1
-- color: 80 + 30
-- size 36 + 37 + 38 + 39 + 42 + 46
SELECT
    criteria.group AS `key`,
    criteria.option AS `value`
FROM articles
    INNER JOIN article_criterias AS criteria ON articles.id = criteria.article_id
    INNER JOIN article_criterias AS criteria_gender 
        ON criteria_gender.article_id = articles.id AND criteria_gender.group = "gender"
    INNER JOIN article_criterias AS criteria_color1 
        ON criteria_color1.article_id = articles.id AND criteria_color1.group = "color"
    INNER JOIN article_criterias AS criteria_size2 
        ON criteria_size2.article_id = articles.id AND criteria_size2.group = "size"
    INNER JOIN article_criterias AS criteria_size3 
        ON criteria_size3.article_id = articles.id AND criteria_size3.group = "size"
    INNER JOIN article_criterias AS criteria_size4 
        ON criteria_size4.article_id = articles.id AND criteria_size4.group = "size"
    INNER JOIN article_criterias AS criteria_size5 
        ON criteria_size5.article_id = articles.id AND criteria_size5.group = "size"
    INNER JOIN article_criterias AS criteria_size6 
        ON criteria_size6.article_id = articles.id AND criteria_size6.group = "size"
    INNER JOIN article_criterias AS criteria_size7 
        ON criteria_size7.article_id = articles.id AND criteria_size7.group = "size"
WHERE
    AND (criteria_gender.option IN ("1"))
    AND (criteria_color1.option IN ("80", "30"))
    AND (criteria_size2.option_val BETWEEN 35.500000 AND 36.500000)
    AND (criteria_size3.option_val BETWEEN 36.500000 AND 37.500000)
    AND (criteria_size4.option_val BETWEEN 37.500000 AND 38.500000)
    AND (criteria_size5.option_val BETWEEN 38.500000 AND 39.500000)
    AND (criteria_size6.option_val BETWEEN 41.500000 AND 42.500000)
    AND (criteria_size7.option_val BETWEEN 45.500000 AND 46.500000)

Answer 1

键/值表真的很麻烦。但是，为了找到某些条件匹配，请聚合您的数据：

select 
  a.*,
  ac.group AS "key",
  ac.option AS "value"
from articles a
join article_criterias ac on ac.article_id = a.article_id
where a.article_id in
(
  select article_id
  from article_criterias
  group by article_id
  having sum("group" = 'gender' and option = '1') > 0
     and sum("group" = 'color' and option in ('30','80')) > 0
     and sum("group" = 'size' and option_val between 35.5 and 36.5) > 0
     and sum("group" = 'size' and option_val between 36.5 and 37.5) > 0
     and sum("group" = 'size' and option_val between 37.5 and 38.5) > 0
     and sum("group" = 'size' and option_val between 38.5 and 39.5) > 0
     and sum("group" = 'size' and option_val between 41.5 and 42.5) > 0
     and sum("group" = 'size' and option_val between 45.5 and 46.5) > 0
)
order by a.article_id, ac.group, ac.option;

这将为您提供所有适用于性别 1、颜色 30 和/或 80 的文章，以及所有列出的尺寸范围，以及它们的所有选项。 （不过，大小范围有点奇怪；例如，大小为 36.5 会满足两个范围。）您明白了：按 article_id 分组并使用 HAVING 以便只获得符合条件的 article_id。

至于你想要的索引

create index idx on article_criterias(article_id, "group", option, option_val);

Answer 2

正如@affan-pathan 所建议的，添加索引确实解决了这个问题：

CREATE INDEX text_option 
ON `article_criterias` (`article_id`, `group`, `option`);

CREATE INDEX numeric_option 
ON `article_criterias` (`article_id`, `group`, `option_val`);

这两个索引将上述查询表单的执行时间从近 1 分钟缩短到不到 50 毫秒！！

Answer 3

我了解您创建的索引解决了您的问题， 但只是为了玩一个伪替代品（避免多个INNER JOIN），你可以尝试这样的事情吗？ （我只测试了三个条件。您的条件应该插入到内部查询中。要仅选择满足所有条件的记录，您必须更改最后一个 WHERE 条件（WHERE max = 3，使用您上面写的条件数；所以如果你使用 5 个条件，你应该写 WHERE max = 5). （我改变了列组和选项的名称，为了我的易用性）。 这只是一个想法，所以请做一些测试并检查性能，请告诉我...

CREATE TABLE CRITERIA (ARTICLE_ID INT, GROU VARCHAR(10), OPT VARCHAR(20), OPTION_VAL NUMERIC(12,2));
CREATE TABLE ARTICLES (ID INT);
INSERT INTO CRITERIA VALUES (100,'size','35',35);
INSERT INTO CRITERIA VALUES (100,'size','36',36);
INSERT INTO CRITERIA VALUES (100,'color','40',40);
INSERT INTO CRITERIA VALUES (100,'gender','1',1);
INSERT INTO CRITERIA VALUES (200,'size','36.2',36.2);
INSERT INTO CRITERIA VALUES (300,'size','36.2',36.2);
INSERT INTO ARTICLES VALUES (100);
INSERT INTO ARTICLES VALUES (200);
INSERT INTO ARTICLES VALUES (300);

-------------------------------------------------------

SELECT D.article_id, D.GROU, D.OPT
FROM (SELECT C.*
     , @o:=CASE WHEN @h=ARTICLE_ID THEN @o ELSE cumul END max
     , @h:=ARTICLE_ID AS a_id
     FROM (SELECT article_id,
             B.GROU, B.OPT,             
             @r:= CASE WHEN @g = B.ARTICLE_ID THEN @r+1 ELSE 1 END cumul,                        
             @g:= B.ARTICLE_ID g                
             FROM CRITERIA B
             CROSS JOIN (SELECT @g:=0, @r:=0) T1
             WHERE (B.GROU='gender' AND B.OPT IN ('1'))
                    OR  (B.GROU='color'  AND B.OPT IN ('40', '30'))
                    OR  (B.GROU='size'   AND B.OPT BETWEEN 35.500000 AND 36.500000)
             ORDER BY article_id
    ) C
CROSS JOIN (SELECT @o:=0, @h:=0) T2
ORDER BY ARTICLE_ID, CUMUL DESC) D
WHERE max=3
;

输出：

article_id  GROU    OPT
100 gender  1
100 color   40
100 size    36