提高linq查询效率

Question

我正在优化我的 Web 应用程序，运行遇到瓶颈，其中从我的 linq 表达式生成的 SQL 非常慢。

以下 SQL 执行时间不到一秒：

SELECT
    ISNULL(COUNT(distinct JOBIDNumber),0),
    ISNULL(SUM(JIMQuantityActual * JIMNetMarginFactor),0),
    ISNULL(sum((isnull(MATRecoverablePercent,0) / 100) * JIMQuantityActual * JIMNetMarginFactor),0),
    ISNULL(sum(CarbonSaving),0)
FROM
    dbo.fn_GetJobsForUser(183486) jb
    inner join cd_JobMaterial on JIMJobId = jb.JOBIDNumber
WHERE
    JOBCollectionDate >= '2014-11-01'

而以下查询的 sql 输出对相同的数据需要 4 到 16 秒：

DateTime d = new DateTime(2014, 11, 1)

from job in sp.sp_GetJobsForUser(183486)
where job.JOBCollectionDate >= d
join material in UnitOfWork.Repository<cd_JobMaterial>().Queryable()
on job.JOBIDNumber equals material.JIMJobId 
group material by 1 into f
select new
{
     Jobs = f.Distinct().Count(),
     Weight = f.Sum(x=> x.JIMQuantityActual * x.JIMNetMarginFactor),
     Carbon = f.Sum(x=> x.CarbonSaving),
     Recovery = f.Sum(x => ((x.MATRecoverablePercent / 100) * x.JIMQuantityActual * x.JIMNetMarginFactor))
}

输出如下：

-- Region Parameters
DECLARE @contactId Int = 183486
DECLARE @p__linq__0 DateTime2 = '2014-11-01 00:00:00.0000000'
-- EndRegion

SELECT
    [Project4].[C1] AS [C1],
    [Project4].[C5] AS [C2],
    [Project4].[C2] AS [C3],
    [Project4].[C3] AS [C4],
    [Project4].[C4] AS [C5]
FROM (SELECT
    [Project2].[C1] AS [C1],
    [Project2].[C2] AS [C2],
    [Project2].[C3] AS [C3],
    [Project2].[C4] AS [C4],
    (SELECT
        COUNT(1) AS [A1]
    FROM (SELECT DISTINCT
        /*Fields omitted for brevity */
    FROM [dbo].[fn_GetJobsForUser](@contactId) AS [Extent3]
    INNER JOIN (SELECT
        /*Fields omitted for brevity */
    FROM [dbo].[cd_JobMaterial] AS [cd_JobMaterial]) AS [Extent4]
        ON [Extent3].[JOBIDNumber] = [Extent4].[JIMJobId]
    WHERE ([Extent3].[JOBCollectionDate] >= @p__linq__0)
    AND ([Project2].[C1] = 1)) AS [Distinct1])
    AS [C5]
FROM (SELECT
    @contactId AS [contactId],
    @p__linq__0 AS [p__linq__0],
    [GroupBy1].[K1] AS [C1],
    [GroupBy1].[A1] AS [C2],
    [GroupBy1].[A2] AS [C3],
    [GroupBy1].[A3] AS [C4]
FROM (SELECT
    [Project1].[K1] AS [K1],
    SUM([Project1].[A1]) AS [A1],
    SUM([Project1].[A2]) AS [A2],
    SUM([Project1].[A3]) AS [A3]
FROM (SELECT
    1 AS [K1],
    [Project1].[JIMQuantityActual] * [Project1].[JIMNetMarginFactor] AS [A1],
    [Project1].[CarbonSaving] AS [A2],
    ([Project1].[MATRecoverablePercent] / CAST(100 AS DECIMAL(18))) * [Project1].[JIMQuantityActual] * [Project1].[JIMNetMarginFactor] AS [A3]
FROM (SELECT
    [Extent2].[MATRecoverablePercent] AS [MATRecoverablePercent],
    [Extent2].[JIMQuantityActual] AS [JIMQuantityActual],
    [Extent2].[JIMNetMarginFactor] AS [JIMNetMarginFactor],
    [Extent2].[CarbonSaving] AS [CarbonSaving]
FROM [dbo].[fn_GetJobsForUser](@contactId) AS [Extent1]
INNER JOIN (SELECT
    /*Fields omitted for brevity */
FROM [dbo].[cd_JobMaterial] AS [cd_JobMaterial]) AS [Extent2]
    ON [Extent1].[JOBIDNumber] = [Extent2].[JIMJobId]
WHERE [Extent1].[JOBCollectionDate] >= @p__linq__0) AS [Project1]) AS [Project1]
GROUP BY [K1]) AS [GroupBy1]) AS [Project2]) AS [Project4]

如何重写 linq 表达式以产生更高效的结果 sql 还是只是编写存储过程并使用它来代替？

Answer 1

不幸的是，这是使用像 Entity Framework 这样灵活的东西的缺点之一，它必须支持各种复杂的翻译。不过，它显然在其他方面也有很大好处，因此您必须在这些方面与性能方面取得平衡。

即使您现在可以找到一种方法来重写生成更好的查询 SQL ，但在未来的版本中，基础提供程序可能会发生变化。在您的应用程序的性能不再可接受之前，尽可能长时间地享受干净、简洁的代码。如果 EF 在那个时候没有削减它，那么使用提供的一些挂钩来执行原始 SQL、存储过程等，这不会那么漂亮。

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