[英]How to make fast GroupBy Query with Condition in Entity Framework
我在Entity Framework中使用GROUP BY
和WHERE
遇到严重的性能问题。
这是罗斯文数据库查询的示例:
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
}
这将生成以下sql:
-- 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]
如您所见, Foo
, Bar
和Baz
作为单独的子查询执行。 每个子查询select
并再次join
。
我期望的是这样的:
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
是否有可能让底层linq提供程序在不使用ctx.Database.SqlQuery<T>
情况下针对这种情况生成更好的SQL?
在我的实际场景中,我们谈论的是7个联接,嵌套分组依据以及更多条件。 EF需要180秒,SQL需要3秒。
如果要在LINQ中对实体(EF6)进行良好的SQL转换,请避免Where
GroupBy
运算符的结果上使用Where
。 尝试改用等效的条件聚合,例如:
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
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