非常慢的MySQL查询
我很乐意接受任何关于这方面的建议——无论是重写查询,还是以不同的方式设置表 我基本上有三个表——产品表、位置表和条件表。位置表存储整个时间段内有关位置的所有信息,与条件相同。这种大规模查询的诀窍是只提取具有最新条件和位置的产品 我从这个问题中得出了大致的想法: 答案是否只是将当前位置和条件存储在主产品表中,并保留这些历史记录表,但不使用它们进行搜索?我喜欢将它们分开的想法,但当然,这个查询需要50秒才能运行,这一点都不实际非常慢的MySQL查询,mysql,sql,join,query-optimization,Mysql,Sql,Join,Query Optimization,我很乐意接受任何关于这方面的建议——无论是重写查询,还是以不同的方式设置表 我基本上有三个表——产品表、位置表和条件表。位置表存储整个时间段内有关位置的所有信息,与条件相同。这种大规模查询的诀窍是只提取具有最新条件和位置的产品 我从这个问题中得出了大致的想法: 答案是否只是将当前位置和条件存储在主产品表中,并保留这些历史记录表,但不使用它们进行搜索?我喜欢将它们分开的想法,但当然,这个查询需要50秒才能运行,这一点都不实际 SELECT '$table' AS tablename, $tab
SELECT
'$table' AS tablename,
$table.id,
product_name,
$table.status,
CL.event AS last_event,
CONCAT_WS(' ', CL.location, CL.floor, CL.bin, CL.bay) AS current_loc,
CC.status AS current_cond
FROM $table
LEFT OUTER JOIN
(SELECT DISTINCT
C.work_type,
C.work_id,
C.status,
C.inspected_timestamp
FROM
(SELECT
CONCAT(work_type, work_id) AS condition_id,
status,
MAX(inspected_timestamp) as current
FROM conditions
GROUP BY condition_id
) XC
JOIN conditions C
on CONCAT(C.work_type, C.work_id) = XC.condition_id
and C.inspected_timestamp = XC.current
) CC ON
$table.id = CC.work_id AND
CC.work_type = '$table'
LEFT OUTER JOIN
(SELECT DISTINCT
L.work_type,
L.work_id,
L.event,
L.location,
L.floor,
L.bin,
L.bay,
L.timestamp
FROM
(SELECT
CONCAT(work_type, work_id) AS location_id,
location,
MAX(timestamp) as current
FROM locations
GROUP BY location_id
) XL
JOIN locations L
on CONCAT(L.work_type, L.work_id) = XL.location_id
and L.timestamp = XL.current
) CL ON
$table.id = CL.work_id AND
CL.work_type = '$table'
HAVING last_event = 'Received'
我在这里添加扩展解释的结果
[0] => Array (
[id] => 1
[select_type] => PRIMARY
[table] => paintings
[type] => ALL
[possible_keys] =>
[key] =>
[key_len] =>
[ref] =>
[rows] => 1159
[filtered] => 100.00
[Extra] => )
[1] => Array (
[id] => 1
[select_type] => PRIMARY
[table] =>
[type] => ALL
[possible_keys] =>
[key] =>
[key_len] =>
[ref] =>
[rows] => 3211
[filtered] => 100.00
[Extra] => )
[2] => Array (
[id] => 1
[select_type] => PRIMARY
[table] =>
[type] => ALL
[possible_keys] =>
[key] =>
[key_len] =>
[ref] =>
[rows] => 1870
[filtered] => 100.00
[Extra] => )
[3] => Array (
[id] => 4
[select_type] => DERIVED
[table] =>
[type] => ALL
[possible_keys] =>
[key] =>
[key_len] =>
[ref] =>
[rows] => 1868
[filtered] => 100.00
[Extra] => Using temporary )
[4] => Array (
[id] => 4
[select_type] => DERIVED
[table] => L
[type] => ref
[possible_keys] => timestamp
[key] => timestamp
[key_len] => 8
[ref] => XL.current
[rows] => 5
[filtered] => 100.00
[Extra] => Using where )
[5] => Array (
[id] => 5
[select_type] => DERIVED
[table] => locations
[type] => ALL
[possible_keys] =>
[key] =>
[key_len] =>
[ref] =>
[rows] => 3913
[filtered] => 100.00
[Extra] => Using temporary; Using filesort )
[6] => Array (
[id] => 2
[select_type] => DERIVED
[table] =>
[type] => ALL
[possible_keys] =>
[key] =>
[key_len] =>
[ref] =>
[rows] => 3191
[filtered] => 100.00
[Extra] => Using temporary )
[7] => Array (
[id] => 2
[select_type] => DERIVED
[table] => C
[type] => ref
[possible_keys] => inspected_timestamp
[key] => inspected_timestamp
[key_len] => 8
[ref] => XC.current
[rows] => 45
[filtered] => 100.00
[Extra] => Using where )
[8] => Array (
[id] => 3
[select_type] => DERIVED
[table] => conditions
[type] => index
[possible_keys] =>
[key] => work_type_2
[key_len] => 316
[ref] =>
[rows] => 3986
[filtered] => 100.00
[Extra] => Using index; Using temporary; Using filesort )
您可以做以下几件事:
我在回答这个问题时纯粹是因为评论长度的限制 我看了你的查询很长一段时间,我认为这主要是它的性质,以及它的编写方式导致查询花费了这么多时间,但我也没有看到任何明显错误的地方 在一些地方,您通过分组获得摘要行,然后将这些查询自连接回来,虽然我不完全理解表或数据的设计,但正如解释所示,这将是非常昂贵的。所以这就是表格扫描。制作临时表并对其进行排序的成本更高,这一点您也是对的 因此,如果这些值是预先汇总并在汇总表中可访问的,并且所花费的时间是不可接受的,那么这些值将有很大帮助。当您查看解释时,请注意行数,因为这会让您很好地了解查询所做的是否合理 此外,根据定义,末尾的having子句也不会被优化。如果有一种方法可以将其移动到where子句或作为其中一个联接中的条件,那么您有机会显著改进查询计划,但考虑到摘要的成本,这仍然需要一些时间
在这一点上,我唯一能建议的是将其分解成小块,看看是否可以优化各个组件,然后重新组装 正如@gview所解释的,有许多因素帮助这个查询变得异常缓慢。除了他在回答中提到的所有这些之外,在两个表中还使用了
CONCAT()
函数,随后将结果用于连接这两个派生表
如果您只想显示表产品
中的行,其中只有位置
中的最新相关行和条件
中的最新相关行,则可以使用以下方法(这只有最新的条件的逻辑,对于最新的位置
,您需要另一个类似的左连接
):
您应该做的第一件事是发出一个解释扩展查询…并包含此信息。显示创建表…对于涉及的表也不会有任何影响。我已经添加了扩展解释结果。感谢您的建议。我看到很多临时表,可能是创建这些表的问题。这是解释扩展
。我添加了解释AIN扩展结果。我没有看到任何表扫描,但有很多派生表和使用临时表。这可能会减慢速度。不过你是对的,我肯定可以缩小一些内部查询。比如,因为我只搜索“已接收”在地理位置上,我可以摆脱所有不属于我的。谢谢,我很感激你的洞察力……而且我会更感激你。TBH,这只是一个答案;)
SELECT
t.id,
t.product_name,
t.status,
cc.status AS current_cond
FROM
$table AS t
LEFT OUTER JOIN
( SELECT c.*
FROM
conditions AS c
JOIN
( SELECT
work_id,
MAX(inspected_timestamp) as current_ts
FROM conditions mc
WHERE work_type = '$table'
GROUP BY condition_id
) AS mc
ON mc.work_id = c.work_id
AND mc.current_ts = c.inspected_timestamp
WHERE c.work_type = '$table'
) AS cc
ON cc.work_id = t.id