Question

我有一个查询尝试查找某个边界框[地理编码查找]中的所有记录。

在通过RedGate探查器运行查询计划后，它在聚集索引扫描（下面）中花费了大量时间（问题底部的违规查询）。这是我运行速度最慢的查询，我猜它有一些问题，因为这最后一步花了这么长时间？

在浏览了SO和Google后，我决定在索引中包含表格的所有列。这是我的索引

PK上的ID。
[UTC_UPDATED Desc，North，East，South，West]上的索引[包括尝试避免扫描的所有其他列]
[UTC_UPDATED Desc，Source Desc]上的索引

查询：

SET ANSI_NULLS ON; SET ANSI_PADDING ON; SET ANSI_WARNINGS ON; SET ARITHABORT OFF; SET CONCAT_NULL_YIELDS_NULL ON; SET NUMERIC_ROUNDABORT OFF; SET QUOTED_IDENTIFIER ON

(@p__linq__0 datetime2(7),@p__linq__1 float,@p__linq__2 float,@p__linq__3 float,@p__linq__4 float)SELECT 
    [Project1].[ID] AS [ID], 
    [Project1].[CENTER] AS [CENTER], 
    [Project1].[BOUNDS] AS [BOUNDS], 
    [Project1].[UTC_UPDATED] AS [UTC_UPDATED], 
    [Project1].[PLACE_ID] AS [PLACE_ID], 
    [Project1].[FORMATTED_ADDRESS] AS [FORMATTED_ADDRESS], 
    [Project1].[POST_CODE] AS [POST_CODE], 
    [Project1].[SOURCE] AS [SOURCE], 
    [Project1].[North] AS [North], 
    [Project1].[East] AS [East], 
    [Project1].[South] AS [South], 
    [Project1].[West] AS [West]
    FROM ( SELECT 
        [Extent1].[ID] AS [ID], 
        [Extent1].[CENTER] AS [CENTER], 
        [Extent1].[BOUNDS] AS [BOUNDS], 
        [Extent1].[UTC_UPDATED] AS [UTC_UPDATED], 
        [Extent1].[PLACE_ID] AS [PLACE_ID], 
        [Extent1].[FORMATTED_ADDRESS] AS [FORMATTED_ADDRESS], 
        [Extent1].[POST_CODE] AS [POST_CODE], 
        [Extent1].[SOURCE] AS [SOURCE], 
        [Extent1].[North] AS [North], 
        [Extent1].[East] AS [East], 
        [Extent1].[South] AS [South], 
        [Extent1].[West] AS [West]
        FROM [dbo].[HST_GEOCODE_POINTS] AS [Extent1]
        WHERE ([Extent1].[UTC_UPDATED] > @p__linq__0) 
            AND ([Extent1].[North] >= @p__linq__1) 
            AND ([Extent1].[East] >= @p__linq__2) 
            AND ([Extent1].[South] <= @p__linq__3) 
            AND ([Extent1].[West] <= @p__linq__4)
    )  AS [Project1]
    ORDER BY [Project1].[UTC_UPDATED] DESC, [Project1].[SOURCE] DESC

注意边界和中心是地理类型。我最初使用Intersects找到正确的地理编码地址，但它太慢我选择使用SQL找到粗糙的NESW边界框[它们只是双倍]然后在代码[.NET]中交叉。

Answer 1

SQL Server是否决定进行扫描或搜索取决于查询的选择性。在您的情况下，扫描比寻找便宜。索引是否涵盖查询不是问题。请阅读tipping point。

为什么我的查询执行聚簇索引扫描

1 个答案: