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[英]Optimizing a MySQL query to avoid “Using temporary” and “Using filesort”
[英]Optimizing a MySQL query to avoid “Using temporary” and “Using filesort”
我知道那里有一千个类似的问题,但是没有一个像我的那样处理复杂的查询(我的MySQL技能还不足以真正理解如何适应它们。)
这里是:
explain select
`ev`.`EventID` AS `EventID`
,`ev`.`EventName` AS `EventName`
,concat(`ev`.`EventDate`,' ',`ev`.`StartTime`) AS `EventDT`
,`ev`.`NumberTicketsAvailable` AS `TotalTickets`
,`ev`.`Soldout` AS `Soldout`
,count((case when (`ec`.`CartStatus` = 'InCart') then 1 else NULL end)) AS `InCartCount`
,count((case when (`ec`.`CartStatus` = 'InPayment') then 1 else NULL end)) AS `InPaymentCount`
,count((case when (`ec`.`CartStatus` = 'Paid') then 1 else NULL end)) AS `PaidCount`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 604800 second) > now())) then 1 else NULL end)) AS `PaidOverWeek`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 432000 second) > now())) then 1 else NULL end)) AS `PaidOverFiveDays`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 86400 second) > now())) then 1 else NULL end)) AS `PaidOverDay`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 43200 second) > now())) then 1 else NULL end)) AS `PaidOverHalfDay`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 21600 second) > now())) then 1 else NULL end)) AS `PaidOverQuarterDay`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 10800 second) > now())) then 1 else NULL end)) AS `PaidOverThreeHours`
,count((case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 3600 second) > now())) then 1 else NULL end)) AS `PaidOverHour`
from (`Events` `ev`
left join (`Events_EventCart_Rel` `eecr`
left join `EventCart` `ec`
on((`eecr`.`EventCartID` = `ec`.`EventCartID`)))
on((`ev`.`EventID` = `eecr`.`EventID`)))
where (`eecr`.`Active` = 1 AND `eecr`.`Deleted` = 'No')
group by
`ev`.`EventID`
,`ev`.`EventName`
,`ev`.`EventDate`
,`ev`.`StartTime`
,`ev`.`NumberTicketsAvailable`
,`ev`.`Soldout`;
结果如下:
+-id-+-select_type-+-table-+--type--+--------possible_keys--------+----key----+-key_len-+----------ref----------+--rows--+---------------------------Extra---------------------------+
| 1| SIMPLE | eecr | index | EventID,EventID_2,EventID_3 | EventID_3 | 10 | {null} | 17609 | Using where; Using index; Using temporary; Using filesort |
| 1| SIMPLE | ev | eq_ref | PRIMARY | PRIMARY | 4 | eecr.EventID | 1 | Using where |
| 1| SIMPLE | ec | eq_ref | PRIMARY | PRIMARY | 4 | eecr.EventCartID | 1 | |
+----+-------------+-------+--------+-----------------------------+-----------+---------+-----------------------+--------+-----------------------------------------------------------+
和表定义:
CREATE TABLE IF NOT EXISTS `Events` (
`EventID` int(10) unsigned NOT NULL AUTO_INCREMENT,
`EventName` varchar(150) NOT NULL,
`StartTime` char(8) NOT NULL DEFAULT '00:00:00',
`EndTime` char(8) NOT NULL DEFAULT '00:00:00',
`EventDate` varchar(20) NOT NULL,
`NumberTicketsAvailable` smallint(6) DEFAULT NULL,
`Soldout` enum('yes','no') DEFAULT 'no',
#...
PRIMARY KEY (`EventID`),
KEY `EndTime` (`EndTime`,`EventDate`),
KEY `StartTime` (`StartTime`,`EventDate`),
KEY `EventDate` (`EventDate`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
CREATE TABLE IF NOT EXISTS `Events_EventCart_Rel` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`EventCartID` int(11) NOT NULL,
`EventID` int(11) NOT NULL,
`DateAdded` datetime NOT NULL,
`PersonID` int(11) NOT NULL,
`SeatTypeID` int(11) NOT NULL,
`MealChoiceID` int(11) NOT NULL,
`Active` tinyint(1) NOT NULL DEFAULT '1',
`Deleted` enum('Yes','No') NOT NULL DEFAULT 'No',
`ModifiedByAdmin` enum('Yes','No') NOT NULL DEFAULT 'No',
PRIMARY KEY (`ID`),
KEY `EventID` (`EventID`,`PersonID`),
KEY `EventCartID` (`EventCartID`),
KEY `EventID_2` (`EventID`),
KEY `EventID_3` (`EventID`,`EventCartID`,`Active`,`Deleted`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
CREATE TABLE IF NOT EXISTS `EventCart` (
`EventCartID` int(11) NOT NULL AUTO_INCREMENT,
`RegistrantsID` int(11) NOT NULL DEFAULT '0',
`DateRecordCreated` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`DateRecordModified` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
`CartStatus` enum('InCart','InPayment','Paid') NOT NULL DEFAULT 'InCart',
`ModifiedByAdmin` enum('yes','no') NOT NULL DEFAULT 'no',
PRIMARY KEY (`EventCartID`),
KEY `rid` (`RegistrantsID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
为了避免任何困惑,请看其中的几列-是的,其中有很多遗留类型的内容,我没有时间来修复。
我发现至少在MySQL中,几乎所有使用GROUP BY
查询都调用一个临时表。 这就是您巨大的性能成本所在。 尝试使用探查器检查它在哪里花费时间:
编辑:我正在将以下内容SET PROFILING
为SET PROFILING
(不是SET PROFILES
):
SET PROFILING = On;
SELECT ...the whole query you want to profile...
SHOW PROFILES;
SHOW PROFILE FOR QUERY 1;
有关更多详细信息,请参见http://dev.mysql.com/doc/refman/5.1/en/show-profiles.html 。
您没有太多可以解决的方法。 出于性能原因,有时最好消除GROUP BY
和聚合函数:
select
`ev`.`EventID` AS `EventID`
,`ev`.`EventName` AS `EventName`
,concat(`ev`.`EventDate`,' ',`ev`.`StartTime`) AS `EventDT`
,`ev`.`NumberTicketsAvailable` AS `TotalTickets`
,`ev`.`Soldout` AS `Soldout`
,case when (`ec`.`CartStatus` = 'InCart') then 1 else 0 end AS `InCartCounter`
,case when (`ec`.`CartStatus` = 'InPayment') then 1 else 0 end AS `InPaymentCounter`
,case when (`ec`.`CartStatus` = 'Paid') then 1 else 0 end AS `PaidCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 604800 second) > now())) then 1 else 0 end AS `PaidOverWeekCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 432000 second) > now())) then 1 else 0 end AS `PaidOverFiveDaysCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 86400 second) > now())) then 1 else 0 end AS `PaidOverDayCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 43200 second) > now())) then 1 else 0 end AS `PaidOverHalfDayCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 21600 second) > now())) then 1 else 0 end AS `PaidOverQuarterDayCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 10800 second) > now())) then 1 else 0 end AS `PaidOverThreeHoursCounter`
,case when ((`ec`.`CartStatus` = 'Paid') and ((`ec`.`DateRecordModified` + interval 3600 second) > now())) then 1 else 0 end AS `PaidOverHourCounter`
from `Events` `ev`
inner join `Events_EventCart_Rel` `eecr`
on `ev`.`EventID` = `eecr`.`EventID`
inner join `EventCart` `ec`
on `eecr`.`EventCartID` = `ec`.`EventCartID`
where `eecr`.`Active` = 1 and `eecr`.`Deleted` = 'No'
然后,在您的应用程序代码中,获取所有行,并在它们上循环,从而在您进行操作时计算合计计数。 例如在PHP中:
$stmt = $pdo->query($sql);
$events = array();
$counters = array("InCartCounter", "InPaymentCounter", "PaidCounter",
"PaidOverWeekCounter", "PaidOverFiveDaysCounter", "PaidOverDayCounter",
"PaidOverHalfDayCounter", "PaidOverQuarterDayCounter",
"PaidOverThreeHoursCounter", "PaidOverHourCounter");
while ($row = $stmt->fetch())
{
if (!isset($events[$row["EventID"]])) {
$events[$row["EventID"]] = $row;
} else {
foreach ($counters as $key) {
$events[$row["EventID"]][$key] += $row[$key];
}
}
}
它看起来像一个大量的代码,并不厌其烦地做一些SQL 应该能够更有效地完成,但在MySQL的情况下与GROUP BY
编写更多的应用程序代码往往是更好的。
PS:在示例SQL查询中,我将您的联接更改为内部联接。 我认为您不需要外部联接。
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