SQL Server 2005 CTE性能很多逻辑读取

Question

我有一个CTE查询，似乎引起了大量的逻辑读取（或者可能不是）。 我已经运行了SQL Server Profiler跟踪，并且此查询似乎一直导致运行时间最长的查询之一。 （每次点击时都会调用）

基本上，我想知道我的CTE是否正确优化或可以提高。

SET STATISTICS IO ON;
GO
    ;WITH cte (PageId, PageTitle, PageType, PageHeadingId, ParentPage, InNavigation, OrgLevel, SortKey, PageOrder, PathLength, PathName, Active) AS
     (
      SELECT
        PageId, 
        PageTitle,
        PageType,
        PageHeadingId,
        ParentPage, 
        InNavigation,
        0, 
        CAST (PageOrder  AS VARBINARY(200)), 
        PageOrder, 
        0 AS PathLength, 
        CAST('' as varchar(300)) AS PathName,
        Active
       FROM dbo.ContentPage
       WHERE ParentPage = 0
        AND InNavigation = 1
      UNION ALL
      SELECT
        b.PageId, 
        b.PageTitle, 
        b.PageType,
        b.PageHeadingId,
        b.ParentPage,
        b.InNavigation, 
        cte.OrgLevel+1,
        CAST(cte.SortKey + CAST (b.PageOrder AS BINARY(4)) AS VARBINARY(200)),
        b.PageOrder, 
        ((cte.OrgLevel+1) + len('....'+b.PageTitle)) as PathLength,
        CAST ((cte.PathName+'....') AS VARCHAR(300)) AS PathName,
        b.Active
       FROM dbo.ContentPage b
         JOIN cte ON b.ParentPage = cte.PageId
       WHERE b.PageType NOT IN (4, 8, 11, 12, 14)
        -- Remove specific page types from the ContentPage table
     )
    SELECT *, (PathName+PageTitle) AS Hierarchy 
    FROM cte WHERE InNavigation = 1     
    ORDER BY SortKey--, PageOrder
SET STATISTICS IO OFF;
GO

如果我离开这一行：

WHERE b.PageType NOT IN (4, 8, 11, 12, 14)

出来，然后逻辑读取的数量从〜8500跃升至〜13000

（查询的作用是在ASP.NET中建立一个下拉菜单层次结构。）如果逻辑读取正常，那么我想我必须想出另一种方式来缓存/存储该菜单（更新为2或每周3次）

谢谢

ContentPage的表结构

CREATE TABLE [dbo].[ContentPage](
    [PageId] [int] IDENTITY(1,1) NOT NULL,
    [PageTitle] [nvarchar](150) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [PageQuote] [nvarchar](400) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [MetaKeywords] [nvarchar](200) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [MetaDescription] [ntext] COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [PageContent] [ntext] COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Active] [bit] NOT NULL CONSTRAINT [DF_ContentPage_Active]  DEFAULT ((0)),
    [InNavigation] [bit] NOT NULL CONSTRAINT [DF_ContentPage_InNavigation]  DEFAULT ((1)),
    [PageOrder] [int] NOT NULL CONSTRAINT [DF_ContentPage_PageOrder]  DEFAULT ((50)),
    [ParentPage] [int] NOT NULL CONSTRAINT [DF_ContentPage_ParentPage]  DEFAULT ((0)),
    [PageType] [int] NOT NULL CONSTRAINT [DF_ContentPage_PageType]  DEFAULT ((1)),
    [CreatedBy] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [CreatedOn] [datetime] NULL,
    [ModifiedBy] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [ModifiedOn] [datetime] NULL,
    [PageViews] [int] NOT NULL CONSTRAINT [DF_ContentPage_PageViews]  DEFAULT ((0)),
    [Emailed] [int] NOT NULL CONSTRAINT [DF_ContentPage_Emailed]  DEFAULT ((0)),
    [Emailable] [bit] NOT NULL CONSTRAINT [DF_ContentPage_Emailable]  DEFAULT ((1)),
    [Printable] [bit] NOT NULL CONSTRAINT [DF_ContentPage_Printable]  DEFAULT ((1)),
    [ContactButton] [bit] NOT NULL CONSTRAINT [DF_ContentPage_PDFable]  DEFAULT ((0)),
    [PageHeadingId] [int] NULL CONSTRAINT [DF_ContentPage_PadeHeadingId]  DEFAULT ((0)),
    [AlternativeTitle] [nvarchar](150) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [RighthandImage] [nvarchar](250) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [IsMicrosite] [bit] NOT NULL CONSTRAINT [DF_ContentPage_IsMicrosite]  DEFAULT ((0)),
 CONSTRAINT [PK_ContentPage] PRIMARY KEY CLUSTERED 
(
    [PageId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

Answer 1

您的CTE使用内部的JOIN本身-因此这里存在某种外键关系：

FROM dbo.ContentPage b
JOIN cte ON b.ParentPage = cte.PageId

因此，在b.ParentPage上有一个索引，在PageId上有另一个索引可能会有所帮助。

同样，您的查询在b.PageType和InNavigation上具有WHERE子句，因此您应考虑在PageType上PageType索引（或可能将(PageType, InNavigation)组合在一起）。

此外，你通过排序SortKey这是基于PageOrder等等，一个指数也可能是有用的。

尝试一次创建一个索引，重新运行查询，比较统计数据和数字-然后确定哪些确实对您有利（哪些没有）。 索引并不是一门精确的科学-您不能总是预测出什么有帮助和有用，什么没有用-您必须尝试一下并将其与原始查询进行比较，然后再确定有帮助和无用。