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关于系统： - 有创建课程和包的导师 - 正在遵循基于标签的搜索方法。当新导师注册和导师创建包时创建标签关系（这使得导师和包可搜索）。有关详细信息，请查看标签在此系统中的工作原理部分？以下。

以下是有关查询

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，查询所花费的时间惊人地上升，而对于我拥有的当前数据，与订单的正常查询时间相比，它大约是 25 秒0.005 - 0.0002 秒，这使得它完全无法使用。

由于尚未对所有可能的字段进行索引，因此可能会导致一些延迟。标签表的标签字段被索引。查询有问题吗？执行时间超过 20 秒的原因是什么？

标签在这个系统中是如何工作的？

  • 当导师注册时，会输入标签并根据导师的详细信息（如姓名、姓氏等）创建标签关系。
  • 当导师创建包时，再次输入标签并根据包的详细信息（如包名称、描述等）创建标签关系。
  • 存储在tutors_tag_relations 中的导师的标签关系和存储在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：- 请看这个截图 - http://www.test.examvillage.com/Explain_query.jpg

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3 回答 3

2

您可能会看到它是否有助于在以下字段上添加索引：

lptagrels.id_tutor
wtagrels.id_tutor
od.id_author

然后尝试摆脱case-whenwhere 子句中的结构。您可以直接添加一些特定于表的限制来加入，例如：left join t2 on t1.id = t2.id AND ...使代码更具可读性。

编辑： 似乎你在这里有一个错误的方法：你搜索所有标签，然后计算匹配搜索的标签。相反，您应该搜索匹配的标签，然后计算具有这些标签的结果。

于 2010-06-09T08:38:34.573 回答
1

我最近遇到了类似的问题。我必须修改查询以实现新功能，这意味着添加多个连接和左连接。逻辑是正确实现的，但是对于一些更大的表来说，它需要很长时间。

正如布赖恩建议的那样，解决方案是完全重写。

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出现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
  • 最后对该临时表执行查询以提取最终结果

所有这些都是在一个存储过程中完成的，最终结果已经通过了单元测试，并且速度非常快。

更新

请测试此查询，看看它是否返回与原始相同的结果。如果是这样，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
于 2010-06-09T10:00:55.287 回答
0

把这段代码从后面拿出来拍。

然后重新开始。

我不是轻率，但这太可怕了，你会为你自己和其他任何人在未来触摸它，现在摆脱它是一个很大的帮助。

于 2010-06-09T08:42:22.407 回答