我如何通过多个自我连接和索引加快我的Moodle MySQL查询

Question

我已经创建了一个查询，其中有多个与多个表获取数据获取数据的查询。对于5000多个记录，其工作速度非常慢。我检查了检查，并适当地为查询中使用的每个表格设置了索引。我试图通过多个选项来优化此查询，但它不起作用，我也不完全理解解释或解释扩展的帮助。

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查询

EXPLAIN EXTENDED
SELECT @rownum := @rownum + 1 AS id,
       u.id AS userid,
       u.username AS employeeid,
       u.firstname,
       u.lastname,
       u.email AS email,
       u.city AS state,
       c.fullname AS course,
       c.id AS courseid,
       c.fullname AS coursename,
       fi2.data branchid,
       fi3.data branchname,
       fi6.data areaname,
       fi7.data regname,
       fi8.data designation,
       fi9.data department,
       fi10.data zone,
       fi11.data branchcategory,
       fi12.data branchdistrict,
       fi13.data branchstate,
       fi17.data gender,
       fi21.data employeecategory,
       fi22.data persontype,
       fi23.data assignmentstatus,
       fi30.data POSITION,
       fi32.data dateofjoining,
       fi33.data dateofbirth,
       st.scoid,
       st.scormid,
       st.attempt,
       st.value cmistarttime,
       st5.value cmilessonstatus,
       st5.timemodified cmitimemodified,
       st3.value cmitotaltime,
       st2.value cmiscore
FROM (
       SELECT @rownum := 0
     ) r,
     mdl_user u
     JOIN mdl_role_assignments ra ON ra.userid = u.id
     JOIN mdl_context ctx ON ctx.id = ra.contextid
     JOIN mdl_course c ON c.id = ctx.instanceid
     JOIN mdl_scorm s ON s.course = c.id
     JOIN mdl_scorm_scoes_track st ON st.scormid = s.id AND st.userid = u.id
     JOIN mdl_scorm_scoes_track AS st2 ON (u.id = st2.userid AND st2.scormid
       = s.id AND st2.scoid = st.scoid AND st2.attempt = st.attempt)
     JOIN mdl_scorm_scoes_track AS st3 ON (u.id = st3.userid AND st3.scormid
       = s.id AND st3.scoid = st.scoid AND st3.attempt = st.attempt)
     JOIN mdl_scorm_scoes_track AS st5 ON (u.id = st5.userid AND st5.scormid
       = s.id AND st5.scoid = st.scoid AND st5.attempt = st.attempt)
     JOIN mdl_user_info_data AS fi2 ON u.id = fi2.userid
     JOIN mdl_user_info_data AS fi3 ON u.id = fi3.userid
     JOIN mdl_user_info_data AS fi6 ON u.id = fi6.userid
     JOIN mdl_user_info_data AS fi7 ON u.id = fi7.userid
     JOIN mdl_user_info_data AS fi8 ON u.id = fi8.userid
     JOIN mdl_user_info_data AS fi9 ON u.id = fi9.userid
     JOIN mdl_user_info_data AS fi10 ON u.id = fi10.userid
     JOIN mdl_user_info_data AS fi11 ON u.id = fi11.userid
     JOIN mdl_user_info_data AS fi12 ON u.id = fi12.userid
     JOIN mdl_user_info_data AS fi13 ON u.id = fi13.userid
     JOIN mdl_user_info_data AS fi17 ON u.id = fi17.userid
     JOIN mdl_user_info_data AS fi21 ON u.id = fi21.userid
     JOIN mdl_user_info_data AS fi22 ON u.id = fi22.userid
     JOIN mdl_user_info_data AS fi23 ON u.id = fi23.userid
     JOIN mdl_user_info_data AS fi30 ON u.id = fi30.userid
     JOIN mdl_user_info_data AS fi32 ON u.id = fi32.userid
     JOIN mdl_user_info_data AS fi33 ON u.id = fi33.userid
WHERE c.id > 0 AND
      u.id > 0 AND
      u.deleted = 0 AND
      u.suspended = 0 AND
      u.confirmed = 1 AND
      u.id <= 1000 AND
      c.visible = 1 AND
      st.element LIKE '%x.start.time%' AND
      st2.element LIKE '%cmi.core.score.raw%' AND
      st3.element LIKE '%cmi.core.total_time%' AND
      st5.element LIKE '%cmi.core.lesson_status%' AND
      fi2.fieldid = 2 AND
      fi3.fieldid = 3 AND
      fi6.fieldid = 6 AND
      fi7.fieldid = 7 AND
      fi8.fieldid = 8 AND
      fi9.fieldid = 9 AND
      fi10.fieldid = 10 AND
      fi11.fieldid = 11 AND
      fi12.fieldid = 12 AND
      fi13.fieldid = 13 AND
      fi17.fieldid = 17 AND
      fi21.fieldid = 21 AND
      fi22.fieldid = 22 AND
      fi23.fieldid = 23 AND
      fi30.fieldid = 30 AND
      fi32.fieldid = 32 AND
      fi33.fieldid = 33 AND
      ra.roleid = 5 AND
      ctx.contextlevel = 50

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mdl_scorm_scoes_track表

mdl_scorm_scoes_track表

Answer 1

您的4路自加入的目的似乎大致说是要识别4行涉及相同的用户IDS-SCORMID-SCOID-SCOID-ANTEMPT，但具有4个不同的元素。这是获得4个带有4个元素的4个tuples的昂贵方法。（此外，这5列构成了一个唯一的键。）阅读有关关系划分的内容，该截面的sublow值以另一个表中的所有子线值出现，并在SQL中表达它。例如，您需要每4键盘具有不同的元素计数= 4，其中元素在4个值中。

Answer 2

是的，您的假设是正确的。以下是我的查询版本。这是4向自连接，但具有不同的元素。这是标准表，存储了14,00,000多个记录，因此我很难更改表结构或插入查询。

SELECT DISTINCT st1.* FROM mdl_scorm_scoes_track st1
JOIN mdl_scorm_scoes_track st2 ON st1.userid = st2.userid AND st1.scormid = st2.scormid AND st1.scoid = st2.scoid AND st1.attempt = st2.attempt
JOIN mdl_scorm_scoes_track st3 ON st1.userid = st3.userid AND st1.scormid = st3.scormid AND st1.scoid = st3.scoid AND st1.attempt = st3.attempt
JOIN mdl_scorm_scoes_track st4 ON st1.userid = st4.userid AND st1.scormid = st4.scormid AND st1.scoid = st4.scoid AND st1.attempt = st4.attempt
AND st1.element = 'x.start.time' 
AND st2.element = 'cmi.core.score.raw'
AND st3.element = 'cmi.core.total_time'
AND st4.element = 'cmi.core.lesson_status' AND st1.userid <= 10
GROUP BY st1.userid, st1.scormid, st1.scoid, st1.attempt

我也尝试了您建议的方法，但这无济于事。请检查，让我知道我的查询中是否有任何问题

SELECT DISTINCT st1.* FROM mdl_scorm_scoes_track st1
JOIN mdl_scorm_scoes_track st2 ON st1.userid = st2.userid AND st1.scormid = st2.scormid AND st1.scoid = st2.scoid AND st1.attempt = st2.attempt
JOIN mdl_scorm_scoes_track st3 ON st1.userid = st3.userid AND st1.scormid = st3.scormid AND st1.scoid = st3.scoid AND st1.attempt = st3.attempt
JOIN mdl_scorm_scoes_track st4 ON st1.userid = st4.userid AND st1.scormid = st4.scormid AND st1.scoid = st4.scoid AND st1.attempt = st4.attempt
AND st1.element = 'x.start.time' 
AND st2.element = 'cmi.core.score.raw'
AND st3.element = 'cmi.core.total_time'
AND st4.element = 'cmi.core.lesson_status' AND st1.userid <= 10
GROUP BY st1.userid, st1.scormid, st1.scoid, st1.attempt
HAVING COUNT(*) = (
  SELECT COUNT(*) FROM mdl_scorm_scoes_track st5
  WHERE st1.userid = st5.userid AND st1.scormid = st5.scormid AND st1.scoid = st5.scoid AND st1.attempt = st5.attempt AND st5.element = 'x.start.time' 
)