存储过程未使用索引

Question

这个存储过程是 linq 查询执行的结果：我从 Sql Server Profiler 得到它

exec sp_executesql N'SELECT 
[Limit1].[C2] AS [C1], 
[Limit1].[object] AS [object], 
[Limit1].[C1] AS [C2]
FROM ( SELECT TOP (50) 
    [GroupBy1].[A1] AS [C1], 
    [GroupBy1].[K1] AS [object], 
    1 AS [C2]
    FROM ( SELECT 
        [Extent1].[object] AS [K1], 
        COUNT(1) AS [A1]
        FROM [dbo].[BEM_EVT_FULL] AS [Extent1]
        WHERE [Extent1].[date] > @p__linq__0
        GROUP BY [Extent1].[object]
    )  AS [GroupBy1]
)  AS [Limit1]',N'@p__linq__0 datetime2(7)',@p__linq__0='2015-01-21 00:00:00'

我已经在所有列（对象和日期）上创建了索引。问题是这个查询完全忽略了索引，运行时间超过 3 分钟。

另一方面，我有这个手动运行的查询。

SELECT 
[Limit1].[C2] AS [C1], 
[Limit1].[object] AS [object], 
[Limit1].[C1] AS [C2]
FROM ( SELECT TOP (50) 
    [GroupBy1].[A1] AS [C1], 
    [GroupBy1].[K1] AS [object], 
    1 AS [C2]
    FROM ( SELECT 
        [Extent1].[object] AS [K1], 
        COUNT(1) AS [A1]
        FROM [dbo].[BEM_EVT_FULL] AS [Extent1]
        WHERE [Extent1].[date] > convert(datetime2, '2015-01-21 00:00:00.0000000', 121)
        GROUP BY [Extent1].[object]
    )  AS [GroupBy1]
)  AS [Limit1]

此查询受益于索引并在 1 秒内运行。有谁知道这是为什么？

Answer 1

我觉得添加 OPTION(RECOMPILE) 会对您有所帮助。问题是实体框架如何做到这一点。看看这个链接Adding a query hint when calling Table-Valued Function

exec sp_executesql 
    N'SELECT    [Limit1].[C2] AS [C1], 
                [Limit1].[object] AS [object], 
                [Limit1].[C1] AS [C2]
    FROM 
    (
        SELECT TOP (50) [GroupBy1].[A1] AS [C1], 
                        [GroupBy1].[K1] AS [object], 
                        1 AS [C2]
        FROM 
        (
            SELECT 
            [Extent1].[object] AS [K1], 
            COUNT(1) AS [A1]
            FROM [dbo].[BEM_EVT_FULL] AS [Extent1]
            WHERE [Extent1].[date] > @p__linq__0
            GROUP BY [Extent1].[object]
        )  AS [GroupBy1]
    )  AS [Limit1]
    OPTION (RECOMPILE)',

    N'@p__linq__0 datetime2(7)',
    @p__linq__0='2015-01-21 00:00:00'