优化实体框架Linq查询（选择了1个意外字段）

Question

All,

Can anyone help me optimize the following EF/Linq query:

The EF/Linq query (taken from 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()

The relation between Articles and Services ( ks.Service.SAPProductNumber == a.SAPProductNumber ) is in theory a 1:optional relation with cannot be defined in EF. This is however not my question.

The resulting SQL query:

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]

Why does EF generate a query that selects [Join1].[F_SERVICESID]? I don't need this field. Does anyone know a way to prevent this?

Kind regards, Jan.

ADDITION 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()

results in:

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]

This 'improvement' does not answer my own question, but the result surely looks prettier to me.

UPDATE 1:

The query in Ivan Stoev's answer produces the following 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

Why does EF generate a query that selects [Join1].[F_SERVICESID]? I don't need this field.

That's weird if true, I have no explanation for that.

Can anyone help me optimize the following EF/Linq query

It's worth trying the following, which for me represents the most logical way to retrieve the data in question:

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()

UPDATE: Recently I've encountered that EF includes some additional fields in the generated SQL query when dialing with foreign key relations. These fields are not included in the projected result, so I think you should not worry about. Take any of the queries above, execute it inside the real code environment (VS Debug) and check the the projected list - I'm pretty sure the field in question will not be there.