优化 Entity Framework Linq 查询（选择 1 个意外字段）

Question

全部，

谁能帮我优化以下 EF/Linq 查询：

EF/Linq 查询（取自 LinqPad）：

Articles
    .AsNoTracking()
    .Where(a => a.Active == "J")
    .SelectMany(a => KerlServices
        .Where(ks => ks.Service.SAPProductNumber == a.SAPProductNumber))
    .Select(ks => new {
        ks.KerlCode,
        ks.Service.SAPProductNumber,
        ks.Service.Type })
    .ToList()

Articles 和 Services (ks.Service.SAPProductNumber == a.SAPProductNumber) 之间的关系理论上是 1:optional 关系 with 不能在 EF 中定义。然而，这不是我的问题。

生成的 SQL 查询：

SELECT 
    [Join1].[F_SERVICESID] AS [F_SERVICESID], 
    [Join1].[F_KERLCOD] AS [F_KERLCOD], 
    [Join1].[F_SAPARTNUM] AS [F_SAPARTNUM], 
    [Join1].[F_TYPE] AS [F_TYPE]
    FROM  [dbo].[T_ART] AS [Extent1]
    INNER JOIN  (SELECT [Extent2].[F_KERLCOD] AS [F_KERLCOD], [Extent2].[F_SERVICESID] AS [F_SERVICESID], [Extent3].[F_SAPARTNUM] AS [F_SAPARTNUM], [Extent3].[F_TYPE] AS [F_TYPE]
        FROM  [dbo].[T_SERVICESKERL] AS [Extent2]
        INNER JOIN [dbo].[T_SERVICES] AS [Extent3] ON [Extent2].[F_SERVICESID] = [Extent3].[F_ID] ) AS [Join1] ON [Extent1].[F_SAPARTNUM] = [Join1].[F_SAPARTNUM]
    WHERE N'J' = [Extent1].[F_ACTIND]

为什么 EF 会生成选择 [Join1].[F_SERVICESID] 的查询？我不需要这个字段。有谁知道防止这种情况的方法吗？

亲切的问候，简。

附加 1：

KerlServices
    .AsNoTracking()
    .Select(ks => new {
        ks.KerlCode,
        ks.Service.SAPProductNumber,
        ks.Service.Type })
    .Join(
        Articles,
        ks => ks.SAPProductNumber,
        a => a.SAPProductNumber,
        (ks, a) => new { ks, a.Active })
    .Where(ksa => ksa.Active == "J")
    .Select(ksa => ksa.ks)
    .ToList()

结果：

SELECT 
    [Extent1].[F_SERVICESID] AS [F_SERVICESID], 
    [Extent1].[F_KERLCOD] AS [F_KERLCOD], 
    [Extent2].[F_SAPARTNUM] AS [F_SAPARTNUM], 
    [Extent2].[F_TYPE] AS [F_TYPE]
    FROM   [dbo].[T_SERVICESKERL] AS [Extent1]
    INNER JOIN [dbo].[T_SERVICES] AS [Extent2] ON [Extent1].[F_SERVICESID] = [Extent2].[F_ID]
    INNER JOIN [dbo].[T_ART] AS [Extent3] ON [Extent2].[F_SAPARTNUM] = [Extent3].[F_SAPARTNUM]
    WHERE N'J' = [Extent3].[F_ACTIND]

这个“改进”没有回答我自己的问题，但结果对我来说肯定看起来更漂亮。

更新 1：

Ivan Stoev 的回答中的查询产生以下 SQL：

SELECT 
    [Extent1].[F_SERVICESID] AS [F_SERVICESID], 
    [Extent1].[F_KERLCOD] AS [F_KERLCOD], 
    [Extent2].[F_SAPARTNUM] AS [F_SAPARTNUM], 
    [Extent2].[F_TYPE] AS [F_TYPE]
    FROM  [dbo].[T_SERVICESKERL] AS [Extent1]
    INNER JOIN [dbo].[T_SERVICES] AS [Extent2] ON [Extent1].[F_SERVICESID] = [Extent2].[F_ID]
    WHERE  EXISTS (SELECT 
        1 AS [C1]
        FROM [dbo].[T_ART] AS [Extent3]
        WHERE (N'J' = [Extent3].[F_ACTIND]) AND ([Extent3].[F_SAPARTNUM] = [Extent2].[F_SAPARTNUM])
    )

Answer 1

为什么 EF 会生成选择 [Join1].[F_SERVICESID] 的查询？我不需要这个字段。

如果是真的那很奇怪，我对此没有任何解释。

谁能帮我优化以下 EF/Linq 查询

值得尝试以下方法，这对我来说代表了检索相关数据的最合乎逻辑的方式：

KerlServices
    .AsNoTracking()
    .Select(ks => new {
        ks.KerlCode,
        ks.Service.SAPProductNumber,
        ks.Service.Type })
    .Where(ks => Articles.Any(a => a.Active == "J" && a.SAPProductNumber == ks.SAPProductNumber)
    .ToList()

更新： 最近我发现 EF 在使用外键关系拨号时在生成的 SQL 查询中包含一些附加字段。这些字段不包含在投影结果中，所以我认为您不必担心。采取上述任何查询，在真实代码环境（VS 调试）中执行它并检查投影列表 - 我很确定相关字段不会存在。