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我正在使用以下查询，正如您从下面的结果中看到的那样，返回结果需要 2 个多小时。我很想知道如何加快速度——我相信我已经正确地建立了索引，但是返回这些数据仍然需要大量的时间。

EXPLAIN SELECT Import_Values.base_vehicle_id,
    Import_Values.qty,
    Import_Values.part_type_id,
    Import_Values.part_id,
    Import_Values.position_id,
    Import_Values.note,
    Parts.partterminologyname,
    BaseVehicle.YearID,
    Make.MakeName,
    Model.modelname,
    SubModel.SubModelName,
    EngineDesignation.EngineDesignationName,
    EngineVIN.EngineVINName,
    EngineBase.Liter,
    EngineBase.CC,
    EngineBase.CID,
    EngineBase.Cylinders,
    EngineBase.BlockType,
    EngineBase.EngBoreIn,
    EngineBase.EngBoreMetric,
    EngineBase.EngStrokeIn,
    EngineBase.EngStrokeMetric,
    FuelDeliveryType.FuelDeliveryTypeName,
    FuelDeliverySubType.FuelDeliverySubTypeName,
    FuelSystemControlType.FuelSystemControlTypeName,
    FuelSystemDesign.FuelSystemDesignName,
    Aspiration.AspirationName,
    CylinderHeadType.CylinderHeadTypeName,
    FuelType.FuelTypeName,
    IgnitionSystemType.IgnitionSystemTypeName,
    Mfr.MfrName,
    EngineVersion.EngineVersion,
    Valves.ValvesPerEngine,
    BedLength.BedLength,
    BedLength.BedLengthMetric,
    BedType.BedTypeName
    FROM 
    Import_Values
    INNER JOIN BaseVehicle 
        ON Import_Values.base_vehicle_id=BaseVehicle.BaseVehicleID
    INNER JOIN Parts 
        ON Import_Values.part_type_id=Parts.PartTerminologyID
    INNER JOIN Make
        ON BaseVehicle.MakeID=Make.MakeID
    INNER JOIN Model
        ON BaseVehicle.ModelID=Model.ModelID
    INNER JOIN Vehicle
        ON Import_Values.base_vehicle_id=Vehicle.BaseVehicleID
    INNER JOIN SubModel
        ON Vehicle.SubModelID=SubModel.SubModelID
    INNER JOIN VehicleConfig
        ON Vehicle.VehicleID=VehicleConfig.VehicleID
    INNER JOIN EngineConfig
        ON VehicleConfig.EngineConfigID=EngineConfig.EngineConfigID
    INNER JOIN EngineDesignation
        ON EngineConfig.EngineDesignationID=EngineDesignation.EngineDesignationID
    INNER JOIN EngineVIN
        ON EngineConfig.EngineVINID=EngineVIN.EngineVINID
    INNER JOIN EngineBase
        ON EngineConfig.EngineBaseID=EngineBase.EngineBaseID
    INNER JOIN FuelDeliveryConfig
        ON EngineConfig.FuelDeliveryConfigID=FuelDeliveryConfig.FuelDeliveryConfigID
    INNER JOIN FuelDeliveryType
        ON FuelDeliveryConfig.FuelDeliveryTypeID=FuelDeliveryType.FuelDeliveryTypeID
    INNER JOIN FuelDeliverySubType
        ON FuelDeliveryConfig.FuelDeliverySubTypeID=FuelDeliverySubType.FuelDeliverySubTypeID
    INNER JOIN FuelSystemControlType
        ON FuelDeliveryConfig.FuelSystemControlTypeID=FuelSystemControlType.FuelSystemControlTypeID
    INNER JOIN FuelSystemDesign
        ON FuelDeliveryConfig.FuelSystemDesignID=FuelSystemDesign.FuelSystemDesignID
    INNER JOIN Aspiration
        ON EngineConfig.AspirationID=Aspiration.AspirationID
    INNER JOIN CylinderHeadType
        ON EngineConfig.CylinderHeadTypeID=CylinderHeadType.CylinderHeadTypeID
    INNER JOIN FuelType
        ON EngineConfig.FuelTypeID=FuelType.FuelTypeID
    INNER JOIN IgnitionSystemType
        ON EngineConfig.IgnitionSystemTypeID=IgnitionSystemType.IgnitionSystemTypeID
    INNER JOIN Mfr
        ON EngineConfig.EngineMfrID=Mfr.MfrID
    INNER JOIN EngineVersion
        ON EngineConfig.EngineVersionID=EngineVersion.EngineVersionID
    INNER JOIN Valves
        ON EngineConfig.ValvesID=Valves.Valvesid
    INNER JOIN BedConfig
        ON VehicleConfig.BedConfigID=BedConfig.BedConfigID
    INNER JOIN BedLength
        ON BedConfig.BedLengthID=BedLength.BedLengthID
    INNER JOIN BedType
        ON BedConfig.BedTypeID=BedType.BedTypeID

而结果...

+----+-------------+-----------------------+--------+-----------------------+---------+---------+-----------------------------------------------------------------+--------+-------------------+
| id | select_type | table                 | type   | possible_keys         | key     | key_len | ref                                                             | rows   | Extra             |
+----+-------------+-----------------------+--------+-----------------------+---------+---------+-----------------------------------------------------------------+--------+-------------------+
|  1 | SIMPLE      | VehicleConfig         | ALL    | NULL                  | NULL    | NULL    | NULL                                                            | 171375 |                   |
|  1 | SIMPLE      | Import_Values         | ALL    | base_vehicle_id       | NULL    | NULL    | NULL                                                            |  18933 | Using join buffer |
|  1 | SIMPLE      | BedConfig             | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.VehicleConfig.BedConfigID                  |      1 |                   |
|  1 | SIMPLE      | BedType               | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.BedConfig.BedTypeID                        |      1 |                   |
|  1 | SIMPLE      | BedLength             | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.BedConfig.BedLengthID                      |      1 |                   |
|  1 | SIMPLE      | EngineConfig          | eq_ref | PRIMARY,EngineBaseID  | PRIMARY | 4       | icarcare_importfeeds.VehicleConfig.EngineConfigID               |      1 |                   |
|  1 | SIMPLE      | FuelType              | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.FuelTypeID                    |      1 |                   |
|  1 | SIMPLE      | Valves                | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.ValvesID                      |      1 |                   |
|  1 | SIMPLE      | EngineVIN             | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.EngineVINID                   |      1 |                   |
|  1 | SIMPLE      | EngineVersion         | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.EngineVersionID               |      1 |                   |
|  1 | SIMPLE      | IgnitionSystemType    | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.IgnitionSystemTypeID          |      1 |                   |
|  1 | SIMPLE      | Mfr                   | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.EngineMfrID                   |      1 |                   |
|  1 | SIMPLE      | Aspiration            | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.AspirationID                  |      1 |                   |
|  1 | SIMPLE      | FuelDeliveryConfig    | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.FuelDeliveryConfigID          |      1 |                   |
|  1 | SIMPLE      | FuelSystemDesign      | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.FuelDeliveryConfig.FuelSystemDesignID      |      1 |                   |
|  1 | SIMPLE      | FuelDeliverySubType   | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.FuelDeliveryConfig.FuelDeliverySubTypeID   |      1 |                   |
|  1 | SIMPLE      | EngineDesignation     | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.EngineDesignationID           |      1 |                   |
|  1 | SIMPLE      | EngineBase            | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.EngineBaseID                  |      1 |                   |
|  1 | SIMPLE      | CylinderHeadType      | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.EngineConfig.CylinderHeadTypeID            |      1 |                   |
|  1 | SIMPLE      | Parts                 | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.Import_Values.part_type_id                 |      1 | Using where       |
|  1 | SIMPLE      | FuelSystemControlType | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.FuelDeliveryConfig.FuelSystemControlTypeID |      1 |                   |
|  1 | SIMPLE      | BaseVehicle           | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.Import_Values.base_vehicle_id              |      1 | Using where       |
|  1 | SIMPLE      | Make                  | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.BaseVehicle.MakeID                         |      1 |                   |
|  1 | SIMPLE      | Model                 | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.BaseVehicle.ModelID                        |      1 |                   |
|  1 | SIMPLE      | Vehicle               | eq_ref | PRIMARY,BaseVehicleID | PRIMARY | 4       | icarcare_importfeeds.VehicleConfig.VehicleID                    |      1 | Using where       |
|  1 | SIMPLE      | SubModel              | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.Vehicle.SubModelID                         |      1 |                   |
|  1 | SIMPLE      | FuelDeliveryType      | eq_ref | PRIMARY               | PRIMARY | 4       | icarcare_importfeeds.FuelDeliveryConfig.FuelDeliveryTypeID      |      1 |                   |
+----+-------------+-----------------------+--------+-----------------------+---------+---------+-----------------------------------------------------------------+--------+-------------------+
27 rows in set (2 hours 39 min 30.51 sec)

有什么我可以做的吗？我已经尝试过分析表格、优化它们等。似乎除了让它运行 2 小时之外，还有更多工作要做，哈哈。

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4 回答 4

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您确定您的查询在逻辑上是正确的吗？我对您的数据库一无所知，所以我不知道发生了什么，但这里有一小部分查询似乎与查询中其余查找设置的模式背道而驰。

这里是：

INNER JOIN Vehicle
    ON Import_Values.base_vehicle_id=Vehicle.BaseVehicleID

考虑到您的其余查询，这看起来很奇怪。我本来希望 ON 条件会根据 Vehicle.VehicleID 在 Vehicle 中查找一个条目，这可能是该表中的索引字段。相反，它基于 Vehicle.BaseVehicleID 查找它，这可能是一个未索引的字段。

这完全有可能在逻辑上是正确的。但如果它在逻辑上不正确，它可以解释长时间的延迟。如果事实证明是这种情况，那么您的查询除了需要很长时间才能完成之外，还会提供错误的结果。

编辑：

ImportValues、Vehicle 和 VehicleConfig 之间的关系是什么？一辆车有很多 VehicleConfigs 吗？或者反之亦然？

看起来解释计划最终使用了相当于 ImportValues 和 VehicleConfig 之间的笛卡尔连接的计划。笛卡尔连接产生预期结果是非常不寻常的。无论如何，您可以预期笛卡尔联接需要很长时间。即使查询没有产生笛卡尔连接，如果计划使用相同的算法，它仍然需要很长时间。

第二次编辑：

还有另一个看起来异常的连接条件。是 VehicleConfig 下的加入条件。

INNER JOIN VehicleConfig
        ON Vehicle.VehicleID=VehicleConfig.VehicleID

这是一个很好的连接条件，但不适用于 VehicleConfig 表。它用简单的英语说的是 VehicleConfig 确定 Vehicle。考虑到表和列的名称，这并不奇怪。

但是是什么决定了 VehicleConfig？

如果答案是“什么都没有”，那么除了对 Import_Values 进行全面扫描之外，可怜的旧 MySQL 还在对表进行全面扫描也就不足为奇了。

我的结论： 修复您的查询，以便 27 个表中的 26 个由引用表 PK 的 FK 确定。您的 24 个联接已经满足此标准。当您最终完成并执行解释计划时，您应该只看到一个表在执行全表扫描，即 Import_Values 表。

它应该运行得更快，并且更有可能产生正确的结果。

于 2013-08-02T20:02:51.997 回答
1

在查看您的解释计划时，除了 Import_Values 和 VehicleConfig 之外的所有内容似乎都很好。它甚至看起来都没有考虑 VehicleConfig 的任何键，而是直接进入全表扫描，这很糟糕。

尝试在 VehicleID 和 BedConfigID 上为 VehicleConfig 创建一个复合索引，并在 base_vehicle_id 和 part_type_id 上为 Import_Values 创建一个索引。如果它们已经有索引，则可能只是更新统计信息的问题，您可以使用以下命令执行此操作。希望有帮助。

ANALYZE TABLE VehicleConfig
ANALYZE TABLE Import_Values
于 2013-08-02T18:58:50.357 回答
0

尝试设置 forceplan 并运行查询。另一个建议是将查询分解为多个查询，每个查询中有 6-7 个表连接。

于 2013-08-01T07:56:28.357 回答
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请在执行此查询时尝试应用执行计划，看看是否没有建议任何丢失的键/索引。

于 2013-08-01T07:54:10.880 回答