实体框架 GroupBy 到 Sql 生成

Question

我遇到了 EF 的性能问题。

        using (var context = new CustomDbContext())
        {
            var result = context.
                TransactionLines
                .Where(x => 
                    x.Transaction.TransactionTypeId == 1433 &&
                    (x.Transaction.Eob.EobBatchId == null || x.Transaction.Eob.EobBatch.Status == EobBatchStatusEnum.Completed)
                )
                .GroupBy(x => x.VisitLine.ProcedureId)
                .Select(x => new
                {
                    Id = x.Key,
                    PaidAmount = x.Sum(t => t.PaidAmount),
                    Code = context.Procedures.Where(h => h.Id == x.Key).Select(h => h.Code).FirstOrDefault()
                }).ToArray();
        }

EF生成下一条sql：

SELECT 
1 AS [C1], 
[Project6].[ProcedureId] AS [ProcedureId], 
[Project6].[C2] AS [C2], 
[Project6].[C1] AS [C3]
FROM ( SELECT 
    [Project5].[ProcedureId] AS [ProcedureId], 
    [Project5].[C1] AS [C1], 
    (SELECT 
        SUM([Extent7].[PaidAmount]) AS [A1]
        FROM     [dbo].[TransactionLines] AS [Extent7]
        INNER JOIN [dbo].[Transactions] AS [Extent8] ON [Extent7].[TransactionId] = [Extent8].[Id]
        LEFT OUTER JOIN [dbo].[Eobs] AS [Extent9] ON [Extent8].[EobId] = [Extent9].[Id]
        LEFT OUTER JOIN [dbo].[EobBatches] AS [Extent10] ON [Extent9].[EobBatchId] = [Extent10].[Id]
        LEFT OUTER JOIN [dbo].[VisitLines] AS [Extent11] ON [Extent7].[VisitLineId] = [Extent11].[Id]
        WHERE (([Extent9].[EobBatchId] IS NULL) OR (1 = [Extent10].[Status])) AND ([Extent8].[TransactionTypeId] = 1433) AND (([Project5].[ProcedureId] = [Extent11].[ProcedureId]) OR (([Project5].[ProcedureId] IS NULL) AND ([Extent11].[ProcedureId] IS NULL)))) AS [C2]
    FROM ( SELECT 
        [Project4].[ProcedureId] AS [ProcedureId], 
        [Project4].[C1] AS [C1]
        FROM ( SELECT 
            [Project2].[ProcedureId] AS [ProcedureId], 
            (SELECT TOP (1) 
                [Extent6].[Code] AS [Code]
                FROM [dbo].[Procedures] AS [Extent6]
                WHERE [Extent6].[Id] = [Project2].[ProcedureId]) AS [C1]
            FROM ( SELECT 
                [Distinct1].[ProcedureId] AS [ProcedureId]
                FROM ( SELECT DISTINCT 
                    [Extent5].[ProcedureId] AS [ProcedureId]
                    FROM     [dbo].[TransactionLines] AS [Extent1]
                    INNER JOIN [dbo].[Transactions] AS [Extent2] ON [Extent1].[TransactionId] = [Extent2].[Id]
                    LEFT OUTER JOIN [dbo].[Eobs] AS [Extent3] ON [Extent2].[EobId] = [Extent3].[Id]
                    LEFT OUTER JOIN [dbo].[EobBatches] AS [Extent4] ON [Extent3].[EobBatchId] = [Extent4].[Id]
                    LEFT OUTER JOIN [dbo].[VisitLines] AS [Extent5] ON [Extent1].[VisitLineId] = [Extent5].[Id]
                    WHERE (([Extent3].[EobBatchId] IS NULL) OR (1 = [Extent4].[Status])) AND ([Extent2].[TransactionTypeId] = 1433)
                )  AS [Distinct1]
            )  AS [Project2]
        )  AS [Project4]
    )  AS [Project5]
)  AS [Project6]

查询持续时间约为 3 秒。 如果直接使用 Group By 编写 sql 查询，则查询时长为 1.5 秒，占用的 CPU 资源减少一半。

    SELECT sq.ProcedureId, SUM(sq.PaidAmount), (SELECT TOP(1) Procedures.Code From Procedures Where Procedures.Id = sq.ProcedureId) as Code
FROM(
    SELECT [Extent5].[ProcedureId] AS [ProcedureId],[Extent1].PaidAmount as [PaidAmount]
    FROM     [dbo].[TransactionLines] AS [Extent1]
    INNER JOIN [dbo].[Transactions] AS [Extent2] ON [Extent1].[TransactionId] = [Extent2].[Id]
    LEFT OUTER JOIN [dbo].[Eobs] AS [Extent3] ON [Extent2].[EobId] = [Extent3].[Id]
    LEFT OUTER JOIN [dbo].[EobBatches] AS [Extent4] ON [Extent3].[EobBatchId] = [Extent4].[Id]
    LEFT OUTER JOIN [dbo].[VisitLines] AS [Extent5] ON [Extent1].[VisitLineId] = [Extent5].[Id]
    WHERE (([Extent3].[EobBatchId] IS NULL) OR (1 = [Extent4].[Status])) AND ([Extent2].[TransactionTypeId] = 1433)
) sq
GROUP BY sq.ProcedureId

我编写了不同的 linq，但仍然无法强制 EF 生成 GroupBy 而不是子查询。 理想情况下，我不想使用函数或手动编写 sql，因为我在构建 linq 逻辑时有很多条件。

是否可以强制 EF 完全按照 linq 中编写的方式生成 SQL？

Answer 1

尽量避免

context.Procedures.Where(h => h.Id == x.Key).Select(h => h.Code).FirstOrDefault()

通过在GroupBy 子句中包含Code - 我知道这似乎是多余的，但众所周知，EF 在翻译涉及使用密钥访问器和聚合以外的其他内容的分组操作时遇到问题：

//...
.GroupBy(x => new { Id = x.VisitLine.ProcedureId, x.VisitLine.Procedure.Code })
.Select(x => new
{
    Id = x.Key.Id,
    PaidAmount = x.Sum(t => t.PaidAmount),
    Code = x.Key.Code
}).ToArray();

更新：以上在我的测试环境（最新的EF6.1.3）中生成如下SQL：

SELECT
    1 AS [C1],
    [GroupBy1].[K1] AS [ProcedureId],
    [GroupBy1].[A1] AS [C2],
    [GroupBy1].[K2] AS [Code]
    FROM ( SELECT
        [Extent5].[ProcedureId] AS [K1],
        [Extent6].[Code] AS [K2],
        SUM([Filter1].[PaidAmount]) AS [A1]
        FROM    (SELECT [Extent1].[VisitLineId] AS [VisitLineId], [Extent1].[PaidAmount] AS [PaidAmount]
            FROM    [dbo].[TransactionLine] AS [Extent1]
            INNER JOIN [dbo].[Transaction] AS [Extent2] ON [Extent1].[TransactionId] = [Extent2].[Id]
            LEFT OUTER JOIN [dbo].[Eob] AS [Extent3] ON [Extent2].[EobId] = [Extent3].[Id]
            LEFT OUTER JOIN [dbo].[EobBatch] AS [Extent4] ON [Extent3].[EobBatchId] = [Extent4].[Id]
            WHERE (1433 = [Extent2].[TransactionTypeId]) AND ([Extent3].[EobBatchId] IS NULL OR [Extent4].[Status] = 1) ) AS [Filter1]
        LEFT OUTER JOIN [dbo].[VisitLine] AS [Extent5] ON [Filter1].[VisitLineId] = [Extent5].[Id]
        LEFT OUTER JOIN [dbo].[Procedure] AS [Extent6] ON [Extent5].[ProcedureId] = [Extent6].[Id]
        GROUP BY [Extent5].[ProcedureId], [Extent6].[Code]
    )  AS [GroupBy1]

这比我预期的要好得多。

更新 2： EF 是一头奇怪的野兽。使用双投影会产生预期的结果：

//...
.GroupBy(x => x.VisitLine.ProcedureId)
.Select(x => new
{
    Id = x.Key,
    PaidAmount = x.Sum(t => t.PaidAmount),
})
.Select(x => new
{
    x.Id,
    x.PaidAmount,
    Code = context.Procedures.Where(h => h.Id == x.Id).Select(h => h.Code).FirstOrDefault()
}).ToArray();

产生以下内容：

SELECT
    1 AS [C1],
    [Project2].[ProcedureId] AS [ProcedureId],
    [Project2].[C1] AS [C2],
    [Project2].[C2] AS [C3]
    FROM ( SELECT
        [GroupBy1].[A1] AS [C1],
        [GroupBy1].[K1] AS [ProcedureId],
        (SELECT TOP (1)
            [Extent6].[Code] AS [Code]
            FROM [dbo].[Procedure] AS [Extent6]
            WHERE [Extent6].[Id] = [GroupBy1].[K1]) AS [C2]
        FROM ( SELECT
            [Extent5].[ProcedureId] AS [K1],
            SUM([Filter1].[PaidAmount]) AS [A1]
            FROM   (SELECT [Extent1].[VisitLineId] AS [VisitLineId], [Extent1].[PaidAmount] AS [PaidAmount]
                FROM    [dbo].[TransactionLine] AS [Extent1]
                INNER JOIN [dbo].[Transaction] AS [Extent2] ON [Extent1].[TransactionId] = [Extent2].[Id]
                LEFT OUTER JOIN [dbo].[Eob] AS [Extent3] ON [Extent2].[EobId] = [Extent3].[Id]
                LEFT OUTER JOIN [dbo].[EobBatch] AS [Extent4] ON [Extent3].[EobBatchId] = [Extent4].[Id]
                WHERE (1433 = [Extent2].[TransactionTypeId]) AND ([Extent3].[EobBatchId] IS NULL OR [Extent4].[Status] = 1) ) AS [Filter1]
            LEFT OUTER JOIN [dbo].[VisitLine] AS [Extent5] ON [Filter1].[VisitLineId] = [Extent5].[Id]
            GROUP BY [Extent5].[ProcedureId]
        )  AS [GroupBy1]
    )  AS [Project2]

附：如果不清楚，请回答您的具体问题

是否可以强制 EF 完全按照 linq 中编写的方式生成 SQL？

没有。相反，您应该以某种方式编写 LINQ 查询以获得所需（或更接近）的 SQL 查询。