Entity Frameworkで条件付き高速GroupByクエリを作成する方法

Question

Entity FrameworkでGROUP BYおよびWHEREに深刻なパフォーマンスの問題があります。ここで

はNorthwind Databaseのためのクエリの例です：

from order in Orders 
join detail in OrderDetails on order.OrderID equals detail.OrderID 
group detail by order.OrderDate into dateGroup 
select new 
{ 
    dateGroup.Key, 
    Foo = dateGroup.Where(e => e.ProductID > 20).Sum(e => (decimal?)e.UnitPrice) ?? 0, 
    Bar = dateGroup.Where(e => e.ProductID > 40).Sum(e => (decimal?)e.UnitPrice) ?? 0, 
    Baz = dateGroup.Where(e => e.ProductID > 60).Sum(e => (decimal?)e.UnitPrice) ?? 0 
} 

これは、次のSQLを生成：あなたは、Foo、BarとBazを見ることができるように

-- Region Parameters 
DECLARE @p0 Int = 20 
DECLARE @p1 Decimal(5,4) = 0 
DECLARE @p2 Int = 40 
DECLARE @p3 Decimal(5,4) = 0 
DECLARE @p4 Int = 60 
DECLARE @p5 Decimal(5,4) = 0 
-- EndRegion 
SELECT [t2].[OrderDate] AS [Key], COALESCE((
    SELECT SUM([t5].[value]) 
    FROM (
     SELECT [t4].[UnitPrice] AS [value], [t4].[ProductID], [t3].[OrderDate] 
     FROM [Orders] AS [t3] 
     INNER JOIN [Order Details] AS [t4] ON [t3].[OrderID] = [t4].[OrderID] 
     ) AS [t5] 
    WHERE ([t5].[ProductID] > @p0) AND ((([t2].[OrderDate] IS NULL) AND ([t5].[OrderDate] IS NULL)) OR (([t2].[OrderDate] IS NOT NULL) AND ([t5].[OrderDate] IS NOT NULL) AND ([t2].[OrderDate] = [t5].[OrderDate]))) 
    ),@p1) AS [Foo], COALESCE((
    SELECT SUM([t8].[value]) 
    FROM (
     SELECT [t7].[UnitPrice] AS [value], [t7].[ProductID], [t6].[OrderDate] 
     FROM [Orders] AS [t6] 
     INNER JOIN [Order Details] AS [t7] ON [t6].[OrderID] = [t7].[OrderID] 
     ) AS [t8] 
    WHERE ([t8].[ProductID] > @p2) AND ((([t2].[OrderDate] IS NULL) AND ([t8].[OrderDate] IS NULL)) OR (([t2].[OrderDate] IS NOT NULL) AND ([t8].[OrderDate] IS NOT NULL) AND ([t2].[OrderDate] = [t8].[OrderDate]))) 
    ),@p3) AS [Bar], COALESCE((
    SELECT SUM([t11].[value]) 
    FROM (
     SELECT [t10].[UnitPrice] AS [value], [t10].[ProductID], [t9].[OrderDate] 
     FROM [Orders] AS [t9] 
     INNER JOIN [Order Details] AS [t10] ON [t9].[OrderID] = [t10].[OrderID] 
     ) AS [t11] 
    WHERE ([t11].[ProductID] > @p4) AND ((([t2].[OrderDate] IS NULL) AND ([t11].[OrderDate] IS NULL)) OR (([t2].[OrderDate] IS NOT NULL) AND ([t11].[OrderDate] IS NOT NULL) AND ([t2].[OrderDate] = [t11].[OrderDate]))) 
    ),@p5) AS [Baz] 
FROM (
    SELECT [t0].[OrderDate] 
    FROM [Orders] AS [t0] 
    INNER JOIN [Order Details] AS [t1] ON [t0].[OrderID] = [t1].[OrderID] 
    GROUP BY [t0].[OrderDate] 
    ) AS [t2] 

を別々のサブクエリとして実行されます。各サブクエリselectおよびjoinが再び発生します。もっとこのようなものです

私が期待している

何か：何とかそれイスト

SELECT 
    Orders.OrderDate, 
    SUM(
    CASE 
     WHEN [Order Details].ProductID > 20 
     THEN [Order Details].UnitPrice 
     ELSE 0 
    END 
) as Foo, 
    SUM(
    CASE 
     WHEN [Order Details].ProductID > 40 
     THEN [Order Details].UnitPrice 
     ELSE 0 
    END 
) as Bar, 
    SUM(
    CASE 
     WHEN [Order Details].ProductID > 60 
     THEN [Order Details].UnitPrice 
     ELSE 0 
    END 
) as Baz 
FROM Orders 
JOIN [Order Details] ON Orders.OrderID = [Order Details].OrderID 
GROUP BY Orders.OrderDate 

可能性はctx.Database.SqlQuery<T>を使用せずに、基本的なLINQプロバイダは、このシナリオのためのより良いSQLを生成させるには？

実際のシナリオでは、7つの結合、ネストされたグループ、さらにはそれ以上の条件について話しています。 EFは180秒、SQLは3秒必要です。

Answer 1

LINQ to Entities（EF6）で適切なSQL変換を行う場合は、WhereをGroupBy演算子の結果に使用しないでください。同等の条件付き集計を代わりに使用してください。例：

Foo = dateGroup.Sum(e => e.ProductID > 20 ? (decimal?)e.UnitPrice : null) ?? 0, 
Bar = dateGroup.Sum(e => e.ProductID > 40 ? (decimal?)e.UnitPrice : null) ?? 0, 
Baz = dateGroup.Sum(e => e.ProductID > 60 ? (decimal?)e.UnitPrice : null) ?? 0