为什么Entity Framework在日期范围查询中不使用日期索引？

Question

我有一个名为BPIrequests的表，其中有28M行，我正在使用Entity Framework查询日期范围。这是它产生超时的查询：

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Request ID] AS [Request ID], 
    [Extent1].[Date] AS [Date], 
    [Extent1].[Lumen URL] AS [Lumen URL], 
    [Extent1].[Copyright owner ID] AS [Copyright owner ID], 
    [Extent1].[Copyright owner name] AS [Copyright owner name], 
    [Extent1].[Reporting organization ID] AS [Reporting organization ID], 
    [Extent1].[Reporting organization name] AS [Reporting organization name], 
    [Extent1].[URLs removed] AS [URLs removed], 
    [Extent1].[URLs that were not in Google's search index] AS [URLs that were not in Google's search index], 
    [Extent1].[URLs for which we took no action] AS [URLs for which we took no action], 
    [Extent1].[URLs pending review] AS [URLs pending review], 
    [Extent1].[From Abuser] AS [From Abuser]
FROM 
    [dbo].[BPIrequests] AS [Extent1]
WHERE 
    ((convert (datetime2, convert(varchar(255), [Extent1].[Date], 102) ,  102)) >= (convert (datetime2, convert(varchar(255), convert(datetime2, '2019-01-11 19:44:10.0000000', 121), 102) ,  102))) 
    AND ((convert (datetime2, convert(varchar(255), [Extent1].[Date], 102) ,  102)) <= (convert (datetime2, convert(varchar(255), convert(datetime2, '2019-01-26 19:44:10.8392197', 121), 102) ,  102)))

如果我在SSMS中将查询编辑为如下所示，它将立即运行：

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Request ID] AS [Request ID], 
    [Extent1].[Date] AS [Date], 
    [Extent1].[Lumen URL] AS [Lumen URL], 
    [Extent1].[Copyright owner ID] AS [Copyright owner ID], 
    [Extent1].[Copyright owner name] AS [Copyright owner name], 
    [Extent1].[Reporting organization ID] AS [Reporting organization ID], 
    [Extent1].[Reporting organization name] AS [Reporting organization name], 
    [Extent1].[URLs removed] AS [URLs removed], 
    [Extent1].[URLs that were not in Google's search index] AS [URLs that were not in Google's search index], 
    [Extent1].[URLs for which we took no action] AS [URLs for which we took no action], 
    [Extent1].[URLs pending review] AS [URLs pending review], 
    [Extent1].[From Abuser] AS [From Abuser]
FROM 
    [dbo].[BPIrequests] AS [Extent1]
WHERE 
    [Extent1].[Date] >= '2019-01-11'
    AND [Extent1].[Date] <= '2019-01-26'

以下是用于比较的查询计划：

如何使Entity Framework使用日期索引？

Answer 1

看起来EF查询中的日期来自一个字符串字段，而sql查询将字符串转换为日期，这使查询优化器感到困惑，并且索引从未得到利用。

您在Management Studio中编写的查询已将值视为日期，因此使用了索引。

您应该更改EF模型类，以将DateTime用作“日期”字段的类型