Question

关于系统： - 有导师创建课程和包 - 正在遵循基于标签的搜索方法。当新教师注册和教师创建包时（这使得教师和包可搜索），创建了标签关系。有关详细信息，请查看标记在此系统中的工作方式部分？下方。

以下是相关查询

SELECT SUM(DISTINCT( t.tag LIKE "%Dictatorship%" )) AS key_1_total_matches,
       SUM(DISTINCT( t.tag LIKE "%democracy%" ))    AS key_2_total_matches,
       COUNT(DISTINCT( od.id_od ))                  AS tutor_popularity,
       CASE
         WHEN ( IF(( wc.id_wc > 0 ), ( wc.wc_api_status = 1
                                       AND wc.wc_type = 0
                                       AND wc.class_date > '2010-06-01 22:00:56'
                                       AND wccp.status = 1
                                       AND ( wccp.country_code = 'IE'
                                              OR wccp.country_code IN ( 'INT' )
                                           ) ), 0)
              ) THEN 1
         ELSE 0
       END                                          AS 'classes_published',
       CASE
         WHEN ( IF(( lp.id_lp > 0 ), ( lp.id_status = 1
                                       AND lp.published = 1
                                       AND lpcp.status = 1
                                       AND ( lpcp.country_code = 'IE'
                                              OR lpcp.country_code IN ( 'INT' )
                                           ) ), 0)
              ) THEN 1
         ELSE 0
       END                                          AS 'packs_published',
       td . *,
       u . *
FROM   tutor_details AS td
       JOIN users AS u
         ON u.id_user = td.id_user
       LEFT JOIN learning_packs_tag_relations AS lptagrels
         ON td.id_tutor = lptagrels.id_tutor
       LEFT JOIN learning_packs AS lp
         ON lptagrels.id_lp = lp.id_lp
       LEFT JOIN learning_packs_categories AS lpc
         ON lpc.id_lp_cat = lp.id_lp_cat
       LEFT JOIN learning_packs_categories AS lpcp
         ON lpcp.id_lp_cat = lpc.id_parent
       LEFT JOIN learning_pack_content AS lpct
         ON ( lp.id_lp = lpct.id_lp )
       LEFT JOIN webclasses_tag_relations AS wtagrels
         ON td.id_tutor = wtagrels.id_tutor
       LEFT JOIN webclasses AS wc
         ON wtagrels.id_wc = wc.id_wc
       LEFT JOIN learning_packs_categories AS wcc
         ON wcc.id_lp_cat = wc.id_wp_cat
       LEFT JOIN learning_packs_categories AS wccp
         ON wccp.id_lp_cat = wcc.id_parent
       LEFT JOIN order_details AS od
         ON td.id_tutor = od.id_author
       LEFT JOIN orders AS o
         ON od.id_order = o.id_order
       LEFT JOIN tutors_tag_relations AS ttagrels
         ON td.id_tutor = ttagrels.id_tutor
       JOIN tags AS t
         ON ( t.id_tag = ttagrels.id_tag )
             OR ( t.id_tag = lptagrels.id_tag )
             OR ( t.id_tag = wtagrels.id_tag )
WHERE  ( u.country = 'IE'
          OR u.country IN ( 'INT' ) )
       AND CASE
             WHEN ( ( t.id_tag = lptagrels.id_tag )
                    AND ( lp.id_lp > 0 ) ) THEN lp.id_status = 1
                                                AND lp.published = 1
                                                AND lpcp.status = 1
                                                AND ( lpcp.country_code = 'IE'
                                                       OR lpcp.country_code IN (
                                                          'INT'
                                                          ) )
             ELSE 1
           END
       AND CASE
             WHEN ( ( t.id_tag = wtagrels.id_tag )
                    AND ( wc.id_wc > 0 ) ) THEN wc.wc_api_status = 1
                                                AND wc.wc_type = 0
                                                AND
             wc.class_date > '2010-06-01 22:00:56'
                                                AND wccp.status = 1
                                                AND ( wccp.country_code = 'IE'
                                                       OR wccp.country_code IN (
                                                          'INT'
                                                          ) )
             ELSE 1
           END
       AND CASE
             WHEN ( od.id_od > 0 ) THEN od.id_author = td.id_tutor
                                        AND o.order_status = 'paid'
                                        AND CASE
             WHEN ( od.id_wc > 0 ) THEN od.can_attend_class = 1
             ELSE 1
                                            END
             ELSE 1
           END
       AND ( t.tag LIKE "%Dictatorship%"
              OR t.tag LIKE "%Democracy%" )
GROUP  BY td.id_tutor
HAVING key_1_total_matches = 1
       AND key_2_total_matches = 1
ORDER  BY tutor_popularity DESC,
          u.surname ASC,
          u.name ASC
LIMIT  0, 20

问题

上述查询返回的结果是正确的（AND逻辑按预期工作），但是对于较重的数据，查询所花费的时间会惊人地增加，而对于当前数据，我认为它与正常查询时间相差25秒大约0.005 - 0.0002秒，这使它完全无法使用。

可能由于所有可能的字段尚未编入索引而导致某些延迟。标记表的标记字段已编制索引。查询有问题吗？ 20多秒执行时间背后的原因是什么？

标签在此系统中的工作方式？

当导师注册时，会输入标签，并根据教师的详细信息（如姓名，姓氏等）创建标签关系。
当教师创建包时，会再次输入标签，并根据包的名称，描述等包的详细信息创建标签关系。
存储在tutors_tag_relations中的教师的标签关系以及存储在learning_packs_tag_relations中的包的标签关系。所有单个标签都存储在标签表中。

解释查询输出： - 请参阅此屏幕截图 - http://www.test.examvillage.com/Explain_query.jpg

Answer 1

您可能会看到它是否有助于在以下字段中添加索引：

lptagrels.id_tutor
wtagrels.id_tutor
od.id_author

然后尝试从where子句中删除case-when结构。您可以直接添加一些特定于表的限制，例如：left join t2 on t1.id = t2.id AND ...，以使代码更具可读性。

修改这里似乎有一个错误的方法：搜索所有标签，然后计算与搜索匹配的标签。相反，您应该搜索匹配的标记，然后计算具有这些标记的结果。

Answer 2

我最近遇到过类似的问题。我不得不修改一个查询来实现一个新功能，这意味着添加几个连接和左连接。逻辑是正确实现的，但它需要一些更大的表格。

解决方案完全重写，正如Brian所说。

我的新方法是这样的：

创建一个临时表，并在此处插入可能最终在最终结果集中的所有相关数据
在此表上运行多个更新，一次加入一个所需的表，而不是同时加入所有表
最后对此临时表执行查询以提取最终结果

所有这些都是在存储过程中完成的，最终结果通过了单元测试，而且速度非常快。

<强>更新

请测试此查询，以查看它是否返回与原始查询相同的结果。如果是，那么我将进一步尝试找到更好的实现。

SELECT SUM(DISTINCT( t.tag LIKE "%Dictatorship%" )) AS key_1_total_matches,
       SUM(DISTINCT( t.tag LIKE "%democracy%" ))    AS key_2_total_matches,
       COUNT(DISTINCT( od.id_od ))                  AS tutor_popularity,
        (wc.id_wc > 0 
        AND wc.wc_api_status = 1
        AND wc.wc_type = 0
        AND wc.class_date > '2010-06-01 22:00:56'
        AND wccp.status = 1
        AND ( wccp.country_code = 'IE' OR wccp.country_code IN ( 'INT' )) 
        ) AS 'classes_published',
        (lp.id_lp > 0  
        AND lp.id_status = 1
        AND lp.published = 1
        AND lpcp.status = 1
        AND ( lpcp.country_code = 'IE' OR lpcp.country_code IN ( 'INT' ) ) 
        ) AS 'packs_published',
       td . *,
       u . *
FROM   tutor_details AS td JOIN users AS u ON u.id_user = td.id_user
            LEFT JOIN order_details AS od                           ON td.id_tutor = od.id_author
                LEFT JOIN orders AS o                               ON od.id_order = o.id_order
            LEFT JOIN learning_packs_tag_relations AS lptagrels     ON td.id_tutor = lptagrels.id_tutor -- 
               LEFT JOIN learning_packs AS lp                       ON lptagrels.id_lp = lp.id_lp
                   LEFT JOIN learning_packs_categories AS lpc       ON lpc.id_lp_cat = lp.id_lp_cat
                       LEFT JOIN learning_packs_categories AS lpcp  ON lpcp.id_lp_cat = lpc.id_parent
                   LEFT JOIN learning_pack_content AS lpct          ON ( lp.id_lp = lpct.id_lp )
            LEFT JOIN webclasses_tag_relations AS wtagrels          ON td.id_tutor = wtagrels.id_tutor  -- 
               LEFT JOIN webclasses AS wc                           ON wtagrels.id_wc = wc.id_wc
                   LEFT JOIN learning_packs_categories AS wcc       ON wcc.id_lp_cat = wc.id_wp_cat
                       LEFT JOIN learning_packs_categories AS wccp  ON wccp.id_lp_cat = wcc.id_parent
            LEFT JOIN tutors_tag_relations AS ttagrels              ON td.id_tutor = ttagrels.id_tutor -- 
        JOIN tags AS t                                              ON ( t.id_tag = ttagrels.id_tag ) 
                                                                        OR ( t.id_tag = lptagrels.id_tag ) 
                                                                        OR ( t.id_tag = wtagrels.id_tag )
WHERE  ( u.country = 'IE' OR u.country IN ( 'INT' ) )
       AND (NOT ( t.id_tag = lptagrels.id_tag AND lp.id_lp > 0) 
            or (lp.id_status = 1
                AND lp.published = 1
                AND lpcp.status = 1
                AND ( lpcp.country_code = 'IE' OR lpcp.country_code IN ('INT') )
                ) 
            )
       AND (not (t.id_tag = wtagrels.id_tag AND wc.id_wc > 0 )
            or (
                wc.wc_api_status = 1
                AND wc.wc_type = 0
                AND wc.class_date > '2010-06-01 22:00:56'
                AND wccp.status = 1
                AND ( wccp.country_code = 'IE' OR wccp.country_code IN ('INT' ) )
                )
            )
       AND (NOT (od.id_od > 0) 
            OR (
                od.id_author = td.id_tutor
                AND o.order_status = 'paid'
                AND (NOT (od.id_wc > 0) OR od.can_attend_class = 1)
                )
        )
       AND ( t.tag LIKE "%Dictatorship%" OR t.tag LIKE "%Democracy%" )
GROUP  BY td.id_tutor
HAVING key_1_total_matches = 1
       AND key_2_total_matches = 1
ORDER  BY tutor_popularity DESC,
          u.surname ASC,
          u.name ASC
LIMIT  0, 20

Answer 3

从后面拿出这个代码并拍摄它。

然后重新开始。

我并不是轻浮，但是这很可怕，你会做自己和其他任何人在未来通过摆脱它而大受欢迎。

Mysql - 帮我优化这个查询（改进的问题）

3 个答案: