[英]MySQL search query with multiple joins and subqueries running slow
我有以下查询,该查询实际上在存储过程中,但是由于存储过程中发生了太多事情,因此将其删除。 基本上,这是最终结果,需要一定的时间(超过一分钟)才能运行,而且我知道原因-从说明的结果中也可以看出-但我无法对它进行排序。
只是为了快速解释此查询在做什么。 它从“连接”到li.nToObjectID = 37
的公司的所有公司获取所有产品。 结果还返回有关其他公司的其他信息,例如其名称,公司ID等。
SELECT DISTINCT
SQL_CALC_FOUND_ROWS
p.id,
p.sTitle,
p.sTeaser,
p.TimeStamp,
p.ExpiryDate,
p.InStoreDate,
p.sCreator,
p.sProductCode,
p.nRetailPrice,
p.nCostPrice,
p.bPublic,
c.id as nCompanyID,
c.sName as sCompany,
m.id as nMID,
m.sFileName as sHighResFileName,
m.nSize,
(
Select sName
FROM tblBrand
WHERE id = p.nBrandID
) as sBrand,
(
Select t.sFileName
FROM tblThumbnail t
where t.nMediaID = m.id AND
t.sType = "thumbnail"
) as sFileName,
(
Select t.nWidth
FROM tblThumbnail t
where t.nMediaID = m.id AND
t.sType = "thumbnail"
) as nWidth,
(
Select t.nHeight
FROM tblThumbnail t
where t.nMediaID = m.id AND
t.sType = "thumbnail"
) as nHeight,
IF (
(
SELECT COUNT(id) FROM tblLink
WHERE
sType = "company"
AND sStatus = "active"
AND nToObjectID = 37
AND nFromObjectID = u.nCompanyID
),
1,
0
) AS bLinked
FROM tblProduct p
INNER JOIN tblMedia m
ON (
m.nTypeID = p.id AND
m.sType = "product"
)
INNER JOIN tblUser u
ON u.id = p.nUserID
INNER JOIN tblCompany c
ON u.nCompanyID = c.id
LEFT JOIN tblLink li
ON (
li.sType = "company"
AND li.sStatus = "active"
AND li.nToObjectID = 37
AND li.nFromObjectID = u.nCompanyID
)
WHERE c.bActive = 1
AND p.bArchive = 0
AND p.bActive = 1
AND NOW() <= p.ExpiryDate
AND (
li.id IS NOT NULL
OR (
li.id IS NULL
AND p.bPublic = 1
)
)
ORDER BY p.TimeStamp DESC
LIMIT 0, 52
单击此处查看EXPLAIN的输出。 抱歉,无法正确设置格式。
http://i60.tinypic.com/2hdqjgj.png
最后,此查询中所有表的行数:
tbl产品数:5392
tbl品牌数:194
公司数量:368
tbl用户数量:416
tbl媒体数:5724
tblLink计数:24800
tbl缩略图计数:22207
因此,我有两个问题:1.是否存在另一种编写此查询的方法,它可能会加快它的速度? 2.我需要tblProducts的哪种索引组合,以便不能搜索所有行?
这是在删除子查询并使用左联接之后的新查询:
SELECT DISTINCT DISTINCT
SQL_CALC_FOUND_ROWS
p.id,
p.sTitle,
p.sTeaser,
p.TimeStamp,
p.ExpiryDate,
p.InStoreDate,
p.sCreator,
p.sProductCode,
p.nRetailPrice,
p.nCostPrice,
p.bPublic,
c.id as nCompanyID,
c.sName as sCompany,
m.id as nMID,
m.sFileName as sHighResFileName,
m.nSize,
brand.sName as sBrand,
thumb.sFilename,
thumb.nWidth,
thumb.nHeight,
IF (
(
SELECT COUNT(id) FROM tblLink
WHERE
sType = "company"
AND sStatus = "active"
AND nToObjectID = 37
AND nFromObjectID = u.nCompanyID
),
1,
0
) AS bLinked
FROM tblProduct p
INNER JOIN tblMedia m
ON (
m.nTypeID = p.id AND
m.sType = "product"
)
INNER JOIN tblUser u
ON u.id = p.nUserID
INNER JOIN tblCompany c
ON u.nCompanyID = c.id
LEFT JOIN tblLink li
ON (
li.sType = "company"
AND li.sStatus = "active"
AND li.nToObjectID = 37
AND li.nFromObjectID = u.nCompanyID
)
LEFT JOIN tblBrand AS brand
ON brand.id = p.nBrandID
LEFT JOIN tblThumbnail AS thumb
ON (
thumb.nMediaID = m.id
AND thumb.sType = 'thumbnail'
)
WHERE c.bActive = 1
AND p.bArchive = 0
AND p.bActive = 1
AND NOW() <= p.ExpiryDate
AND (
li.id IS NOT NULL
OR (
li.id IS NULL
AND p.bPublic = 1
)
)
ORDER BY p.TimeStamp DESC
LIMIT 0, 52;
ALTER TABLE tblThumbnail ADD INDEX (nMediaID,sType) USING BTREE;
ALTER TABLE tblMedia ADD INDEX (nTypeID,sType) USING BTREE;
ALTER TABLE tblProduct ADD INDEX (bArchive,bActive,ExpiryDate,bPublic,TimeStamp) USING BTREE;
完成上述更改后,说明显示现在仅在tblProduct上搜索1464行,而不是5392行。
这是一个很大的查询,正在进行中。 将需要一些步骤来对其进行优化。 我将只介绍几个步骤。
第一步。 您可以摆脱SQL_CALC_FOUND_ROWS并仍然使程序正常工作吗? 如果是这样,请执行此操作。 当您指定SQL_CALC_FOUND_ROWS时,有时意味着服务器必须延迟将结果集的第一行发送给您,直到最后一行可用为止。
第二步。 将依赖子查询重构为JOIN。
这是您可能的处理方式。 您查询的一部分看起来像这样...
SELECT DISTINCT SQL_CALC_FOUND_ROWS
p.id,
...
c.id as nCompanyID,
...
m.id as nMID,
...
( /* dependent subquery to be removed */
Select sName
FROM tblBrand
WHERE id = p.nBrandID
) as sBrand,
( /* dependent subquery to be removed */
Select t.sFileName
FROM tblThumbnail t
where t.nMediaID = m.id AND
t.sType = "thumbnail"
) as sFileName,
( /* dependent subquery to be removed */
Select t.nWidth
FROM tblThumbnail t
where t.nMediaID = m.id AND
t.sType = "thumbnail"
) as nWidth,
( /* dependent subquery to be removed */
Select t.nHeight
FROM tblThumbnail t
where t.nMediaID = m.id AND
t.sType = "thumbnail"
) as nHeight,
...
试试这个吧。 请注意品牌和缩略图相关子查询如何消失。 缩略图有三个相关的子查询。 它们可以消失为单个JOIN。
SELECT DISTINCT SQL_CALC_FOUND_ROWS
p.id,
...
brand.sName,
thumb.sFilename,
thumb.nWidth,
thumb.nHeight,
...
FROM tblProduct p
INNER JOIN tblMedia AS m ON (m.nTypeID = p.id AND m.sType = 'product')
... (other table joins) ...
LEFT JOIN tblBrand AS brand ON p.id = p.nBrandID
LEFT JOIN tblMedia AS thumb ON (t.nMediaID = m.id AND thumb.sType = 'thumbnail')
我使用LEFT JOIN而不是INNER JOIN,所以如果缺少所连接的行,MySQL将显示NULL值。
编辑
您正在使用如下所示的联接模式:
JOIN sometable AS s ON (s.someID = m.id AND s.sType = 'string')
您似乎在几个表上执行此操作。 您可能可以通过在那些表中创建复合索引来加快JOIN操作。 例如,尝试将以下索引添加到tblThumbnail:(sType,nMediaID)。 您可以使用此DDL语句执行此操作。
ALTER TABLE tblThumbnail ADD INDEX (sType, nMediaID) USING BTREE
您可以使用相同的连接模式对其他表执行类似的操作。
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