优化实体框架 Linq 查询(选择 1 个意外字段)
本文关键字:意外 字段 选择 实体 框架 Linq 查询 优化 | 更新日期: 2023-09-27 18:17:44
All,
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()
文章和服务(ks.Service.SAPProductNumber == a.SAPProductNumber
(之间的关系在理论上是1:可选的关系,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] 的查询。[F_SERVICESID]?我不需要这个字段。有谁知道防止这种情况的方法?
亲切的问候,一月。
加法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()
结果在:
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]
这种"改进"并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 答案中的查询生成以下 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])
)
为什么 EF 会生成选择 [Join1] 的查询。[F_SERVICESID]?我不需要这个字段。
如果这是真的,那就很奇怪了,我对此没有任何解释。
谁能帮我优化以下EF/Linq查询
值得尝试以下内容,对我来说,这代表了检索相关数据的最合乎逻辑的方法:
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:最近我遇到EF在使用外键关系拨号时在生成的SQL查询中包含一些其他字段。这些字段不包括在预测结果中,因此我认为您不必担心。获取上面的任何查询,在实际代码环境(VS Debug(中执行它并检查投影列表 - 我很确定有问题的字段不会在那里。