Question

我有一个查询，需要15秒才能在MySQL 5.6 Server中获得350个结果，但我无法诊断原因，我对数据库优化还是很陌生。

EXPLAIN视觉效果确实显示了一些非唯一键查询 here ，但每个键查询只显示1行。

我无法解释表格形式的解释，我希望其他人可以在这里看起来像 this 。

我尝试将结尾LIMIT = 350切换为100、10，查询运行的时间完全相同，大约为15秒。

我尝试过合并视图，但是除了很难重新创建此查询之外，它并没有提高性能。

也许相关，在我们的MySQL数据库中的其他EXPLAIN语句中，我已经看到一个在其旁边引用了Materialized的视图，但是该查询中所使用的三个视图中的任何一个都没有出现在该视图附近甚至根本看不到所引用的视图，而只看到它们所引用的表。这是一个因素吗？

我最后的尝试是用特定的列替换最后选择的列listlineitems.*，因为我读过这可以提高速度，并且是更好的做法，但是我有一种绝望的感觉大大改善了这种情况。

这是查询-

SELECT 
0 AS 'Check',
DATE_FORMAT(`listlineitems`.`dateEntered`,
        '%Y-%m-%d') AS 'Date Entered',
`listlineitems`.`itemId` AS 'parentTableIdx',
`listlineitems`.`parentProjectId` AS 'parentProjectIdx',
`listlineitems`.`idx` AS 'ID',
IF(`listlineitems`.`active` = 1,
    'Active',
    'Inactive') AS 'Active/Inactive',
CONCAT(`listUsers`.`FirstName`,
        ' ',
        `listUsers`.`LastName`) AS 'Employee',
CASE `listlineitems`.`type`
    WHEN 1 THEN 'Time Entry'
    WHEN 2 THEN 'Expense Entry'
END AS 'Type',
`listcustomers`.`name` AS 'Customer',
`listlocations`.`name` AS 'Location',
`listareas`.`name` AS 'Area',
`listassets`.`name` AS 'Asset',
`listprojects`.`name` AS 'Project',
`listprojects`.`number` 'Project #',
`listprojects`.`autoassign` 'autoassign',
`listactivities`.`name` AS 'Activity',
(CASE `listlineitems`.`type`
    WHEN 1 THEN `listlineitems`.`qty`
    WHEN 2 THEN `listlineitems`.`qty`
END) AS 'Quantity',
`listlineitems`.`taxable` AS 'Taxable',
`listlineitems`.`totalAmount` - `listlineitems`.`taxAmount` AS 'Pre-Tax Amount',
`listlineitems`.`taxAmount` AS 'Tax Amount',
`listlineitems`.`totalAmount` AS 'Total Amount',
`listCustomers`.`idx` AS 'parentCustomerIdx',
`listLocations`.`idx` AS 'parentLocationIdx',
`listAreas`.`idx` AS 'parentAreaIdx',
`listAssets`.`idx` AS 'parentAssetIdx',
CONCAT(`listcustomers`.`name`,
        '/',
        `listlocations`.`name`,
        '/',
        `listareas`.`name`,
        '/',
        `listassets`.`name`,
        '/',
        `listprojects`.`name`) AS 'Path',
IF(`listlineitems`.`customerViewable` = 1,
    'Yes',
    'No') AS 'Cust. Viewable',
(CASE
    WHEN `listlineitems`.`type` = 2 THEN `listexpenseentry`.`TotalCostToPSI` - `listexpenseentry`.`TaxCostToPSI`
    ELSE `listlineitems`.`totalAmount` - `listlineitems`.`taxAmount`
END) AS 'preTaxCostPSI',
(CASE
    WHEN `listlineitems`.`type` = 2 THEN `listexpenseentry`.`TaxCostToPSI`
    ELSE `listlineitems`.`taxAmount`
END) AS 'taxCostPSI',
(CASE
    WHEN `listlineitems`.`type` = 2 THEN `listexpenseentry`.`TotalCostToPSI`
    ELSE `listlineitems`.`totalAmount`
END) AS 'totalCostPSI',
view_solinx2.lastAltered AS 'lastalteredSO',
view_polinx2.lastAlteredPO AS 'lastalteredPO',
view_invlinx2.lastAlteredInv AS 'lastalteredInv',
view_solinx2.lastAlteredAfterConfirmation AS 'lastAlteredAfterConfirmation',
view_solinx2.roleIdSO AS 'roleIdSO',
view_polinx2.roleIdPO AS 'roleIdPO',
view_polinx2.userIdPO AS 'userIdPO',
view_polinx2.lastAlteredafterConfirmation AS 'lastAlteredAfterConfirmationPO',
view_invlinx2.roleIdInv AS 'roleIdInv',
view_invlinx2.userIdInv AS 'userIdInv',
view_invlinx2.lastAlteredafterConfirmation AS 'lastAlteredAfterConfirmationInv',
view_solinx2.roleId AS 'roleId',
view_solinx2.userId AS 'userId',
view_solinx2.soId AS 'SOId',
view_solinx2.autoassignSO AS 'autoassignSO',
IF(view_solinx2.notNeeded = 1,
    'Not Needed',
    view_solinx2.number) AS 'SOname',
view_solinx2.dateEntered AS 'SoDate',
view_solinx2.totalSOAmount AS 'SoTotal',
view_invlinx2.invId AS 'InvId',
IF(view_solinx2.notNeeded = 1,
    '------',
    view_invlinx2.`number`) AS 'InvName',
view_invlinx2.dateEntered AS 'InvDate',
view_invlinx2.amount AS 'InvTotal',
view_polinx2.poId AS 'POId',
IF(view_solinx2.notNeeded = 1,
    '------',
    view_polinx2.`number`) AS 'POName',
view_polinx2.dateEntered AS 'PODate',
view_polinx2.amount AS 'POTotal',
(SELECT 
        listsalesorders.number
    FROM
        listsalesorders
    WHERE
        listsalesorders.idx = autoassign) AS 'test',
`listlineitems`.*
FROM
`listlineitems`
    LEFT JOIN
`listUsers` ON `listlineitems`.`individualId` = `listUsers`.`idx`
    LEFT JOIN
`listprojects` ON `listlineitems`.`parentProjectId` = `listprojects`.`idx`
    LEFT JOIN
`listassets` ON `listlineitems`.`parentAssetId` = `listassets`.`idx`
    LEFT JOIN
`listareas` ON `listlineitems`.`parentAreaId` = `listareas`.`idx`
    LEFT JOIN
`listlocations` ON `listlineitems`.`parentLocationId` = `listlocations`.`idx`
    LEFT JOIN
`listcustomers` ON `listlineitems`.`parentCustomerId` = `listcustomers`.`idx`
    LEFT JOIN
`listactivities` ON `listactivities`.`idx` = `listlineitems`.`activityCode`
    LEFT JOIN
`listexpenseentry` ON (`listexpenseentry`.`idx` = `listlineitems`.`itemId`
    AND `listlineitems`.`type` = 2)
    LEFT JOIN
view_solinx2 ON view_solinx2.idx = listlineitems.idx
    LEFT JOIN
view_polinx2 ON view_polinx2.idx = listlineitems.idx
    LEFT JOIN
view_invlinx2 ON view_invlinx2.idx = listlineitems.idx
GROUP BY `listlineitems`.`idx`
ORDER BY `listlineitems`.`dateEntered` DESC
LIMIT 10;

我无所适从，无法改善这一点，非常感谢任何建议。

Answer 1

您要从listlineitems表（超过100条K记录）中选择所有内容，加入许多表，然后按idx分组，然后抛出大多数结果。

您可以：

尝试将唯一索引（dateEntered，idx）添加到listlineitems
尝试按日期输入限制列表行项目（如果可以接受的话）（WHERE dateEntered> DATE_SUB（NOW（），INTERVAL 30 DAYS））。 dateEntered必须被索引
尝试将listlineitems + grouping + limit中的select放入子查询中，这样MySQL只会对子查询返回的这10行进行联接。
将相关子查询（listsalesorders）转换为左联接

无法解释导致查询缓慢的原因

1 个答案: