Linq在实体框架4中查询.表现糟糕

Question

在我的项目中,我使用EntityFramework 4来处理数据.我通过简单的查询发现了可怕的性能问题.当我在EF4生成的SQL查询中查看分析器时,我感到震惊.

我的实体数据模型中有一些表:

看起来很简单.我正在尝试从指定类别中选择所有相关导航属性的所有产品项目.

我写了这个LINQ查询:

ObjectSet<ProductItem> objectSet = ...; 
int categoryId = ...; 

var res = from pi in objectSet.Include("Product").Include("Inventory").Include("Inventory.Storage") 
where pi.Product.CategoryId == categoryId 
select pi;

EF生成了这个sql查询:

SELECT   [Project1].[pintId1]          AS [pintId], 
[Project1].[pintId]           AS [pintId1], 
[Project1].[intProductId]     AS [intProductId], 
[Project1].[nvcSupplier]      AS [nvcSupplier], 
[Project1].[ nvcArticle]      AS [ nvcArticle], 
[Project1].[nvcBarcode]       AS [nvcBarcode], 
[Project1].[bIsActive]        AS [bIsActive], 
[Project1].[dtDeleted]        AS [dtDeleted], 
[Project1].[pintId2]          AS [pintId2], 
[Project1].[nvcName]          AS [nvcName], 
[Project1].[intCategoryId]    AS [intCategoryId], 
[Project1].[ncProductType]    AS [ncProductType], 
[Project1].[C1]               AS [C1], 
[Project1].[pintId3]          AS [pintId3], 
[Project1].[intProductItemId] AS [intProductItemId], 
[Project1].[intStorageId]     AS [intStorageId], 
[Project1].[dAmount]          AS [dAmount], 
[Project1].[mPrice]           AS [mPrice], 
[Project1].[dtModified]       AS [dtModified], 
[Project1].[pintId4]          AS [pintId4], 
[Project1].[nvcName1]         AS [nvcName1], 
[Project1].[bIsDefault]       AS [bIsDefault] 
FROM     (SELECT [Extent1].[pintId]         AS [pintId], 
[Extent1].[intProductId]   AS [intProductId], 
[Extent1].[nvcSupplier]    AS [nvcSupplier], 
[Extent1].[ nvcArticle]    AS [ nvcArticle], 
[Extent1].[nvcBarcode]     AS [nvcBarcode], 
[Extent1].[bIsActive]      AS [bIsActive], 
[Extent1].[dtDeleted]      AS [dtDeleted], 
[Extent2].[pintId]         AS [pintId1], 
[Extent3].[pintId]         AS [pintId2], 
[Extent3].[nvcName]        AS [nvcName], 
[Extent3].[intCategoryId]  AS [intCategoryId], 
[Extent3].[ncProductType]  AS [ncProductType], 
[Join3].[pintId1]          AS [pintId3], 
[Join3].[intProductItemId] AS [intProductItemId], 
[Join3].[intStorageId]     AS [intStorageId], 
[Join3].[dAmount]          AS [dAmount], 
[Join3].[mPrice]           AS [mPrice], 
[Join3].[dtModified]       AS [dtModified], 
[Join3].[pintId2]          AS [pintId4], 
[Join3].[nvcName]          AS [nvcName1], 
[Join3].[bIsDefault]       AS [bIsDefault], 
CASE 
WHEN ([Join3].[pintId1] IS NULL) THEN CAST(NULL AS int) 
ELSE 1 
END AS [C1] 
FROM   [ProductItem] AS [Extent1] 
INNER JOIN [Product] AS [Extent2] 
ON [Extent1].[intProductId] = [Extent2].[pintId] 
LEFT OUTER JOIN [Product] AS [Extent3] 
ON [Extent1].[intProductId] = [Extent3].[pintId] 
LEFT OUTER JOIN (SELECT [Extent4].[pintId]           AS [pintId1], 
[Extent4].[intProductItemId] AS [intProductItemId], 
[Extent4].[intStorageId]     AS [intStorageId], 
[Extent4].[dAmount]          AS [dAmount], 
[Extent4].[mPrice]           AS [mPrice], 
[Extent4].[dtModified]       AS [dtModified], 
[Extent5].[pintId]           AS [pintId2], 
[Extent5].[nvcName]          AS [nvcName], 
[Extent5].[bIsDefault]       AS [bIsDefault] 
FROM   [Inventory] AS [Extent4] 
INNER JOIN [Storage] AS [Extent5] 
ON [Extent4].[intStorageId] = [Extent5].[pintId]) AS [Join3] 
ON [Extent1].[pintId] = [Join3].[intProductItemId] 
WHERE  [Extent2].[intCategoryId] = 8 /* @p__linq__0 */) AS [Project1] 
ORDER BY [Project1].[pintId1] ASC, 
[Project1].[pintId] ASC, 
[Project1].[pintId2] ASC, 
[Project1].[C1] ASC

对于数据库中的7000条记录和指定类别中的~1000条记录,此查询的执行时间大约为10秒.如果看这个就不足为奇了:

FROM [ProductItem] AS [Extent1]
INNER JOIN [Product] AS [Extent2]
ON [Extent1].[intProductId] = [Extent2].[pintId]
LEFT OUTER JOIN [Product] AS [Extent3]
ON [Extent1].[intProductId] = [Extent3].[pintId]
***LEFT OUTER JOIN (SELECT ....***

嵌套选择加入...可怕......我试图改变LINQ查询,但我得到相同的SQL查询输出.

使用存储过程的解决方案对我来说是不可接受的,因为我正在使用SQL Compact数据库.

Answer 1

你正在做Include("Product").Include("Inventory").Include("Inventory.Storage"),你想知道为什么这么多的记录被提取,为什么这么大的SQL查询？请确保您了解该Include方法的用途.如果您想要更简单的查询,请使用以下内容:

var res =
    from pi in objectSet
    where pi.Product.CategoryId == categoryId 
    select pi;

但请注意,这可能会加载Products,Inventories并且Storages懒惰,这可能会导致在迭代这些子集合时发送更多查询.