如何提高LINQ查询的性能

Question

我有一个查询从一个视图调用TheSQLView - 并加入一个表TheSQLTable - 从该视图获取结果列表。 如果我从视图中获取每条记录，那么将有大约2000个结果。 仅执行此操作大约需要40秒。 即使我使用where子句返回40个结果，它仍然需要大约8秒。

这是一些代码：

using (var db = new SQLEntities(_connStr))
{
   var query = from x in db.TheSQLView
               join y in db.TheSQLTable on x.ID equals y.ID
               select new BSTProject()
               {
                  ID = x.ID,
                  Name = x.Name,
                  ... snipped for brevity (about 12 more properties) ...
                  // The two joined properties
                  PctCompleted = y.PctCompleted == null ? 0 : y.PctCompleted,
                  IsCompleted = y.IsCompleted
               };

   return query.toList();
}

我假设它可能与加入桌面视图有关？

编辑1：运行 SQL事件探查器，此查询正在执行的内容：

SELECT 
[Project1].[IsCompleted] AS [IsCompleted], 
[Project1].[ID] AS [ID], 
[Project1].[Name] AS [Name], 
[Project1].[org_code] AS [org_code], 
[Project1].[GroupName] AS [GroupName], 
[Project1].[clnt_name] AS [clnt_name], 
[Project1].[start_date] AS [start_date], 
[Project1].[PRIcode] AS [PRIcode], 
[Project1].[PRI] AS [PRI], 
[Project1].[PMcode] AS [PMcode], 
[Project1].[PM] AS [PM], 
[Project1].[DPMcode] AS [DPMcode], 
[Project1].[DPM] AS [DPM], 
[Project1].[ADMcode] AS [ADMcode], 
[Project1].[ADM] AS [ADM], 
[Project1].[PhaseBudgetsTotal] AS [PhaseBudgetsTotal], 
[Project1].[PhasesEffortTotal] AS [PhasesEffortTotal], 
[Project1].[PhasesBudgetRemaining] AS [PhasesBudgetRemaining], 
[Project1].[PhasesOver] AS [PhasesOver], 
[Project1].[C1] AS [C1]
FROM ( SELECT 
    [Extent1].[org_code] AS [org_code], 
    [Extent1].[GroupName] AS [GroupName], 
    [Extent1].[ID] AS [ID], 
    [Extent1].[Name] AS [Name], 
    [Extent1].[clnt_name] AS [clnt_name], 
    [Extent1].[start_date] AS [start_date], 
    [Extent1].[PRIcode] AS [PRIcode], 
    [Extent1].[PRI] AS [PRI], 
    [Extent1].[PMcode] AS [PMcode], 
    [Extent1].[PM] AS [PM], 
    [Extent1].[DPMcode] AS [DPMcode], 
    [Extent1].[DPM] AS [DPM], 
    [Extent1].[ADMcode] AS [ADMcode], 
    [Extent1].[ADM] AS [ADM], 
    [Extent1].[PhaseBudgetsTotal] AS [PhaseBudgetsTotal], 
    [Extent1].[PhasesEffortTotal] AS [PhasesEffortTotal], 
    [Extent1].[PhasesBudgetRemaining] AS [PhasesBudgetRemaining], 
    [Extent1].[PhasesOver] AS [PhasesOver], 
    [Extent2].[IsCompleted] AS [IsCompleted], 
    CASE WHEN ([Extent2].[PctCompleted] IS NULL) THEN cast(0 as decimal(18)) ELSE [Extent2].[PctCompleted] END AS [C1]
    FROM  (SELECT 
[TheSQLView].[org_code] AS [org_code], 
[TheSQLView].[GroupName] AS [GroupName], 
[TheSQLView].[ID] AS [ID], 
[TheSQLView].[Name] AS [Name], 
[TheSQLView].[clnt_name] AS [clnt_name], 
[TheSQLView].[start_date] AS [start_date], 
[TheSQLView].[PRIcode] AS [PRIcode], 
[TheSQLView].[PRI] AS [PRI], 
[TheSQLView].[PMcode] AS [PMcode], 
[TheSQLView].[PM] AS [PM], 
[TheSQLView].[DPMcode] AS [DPMcode], 
[TheSQLView].[DPM] AS [DPM], 
[TheSQLView].[ADMcode] AS [ADMcode], 
[TheSQLView].[ADM] AS [ADM], 
[TheSQLView].[PhaseBudgetsTotal] AS [PhaseBudgetsTotal], 
[TheSQLView].[PhasesEffortTotal] AS [PhasesEffortTotal], 
[TheSQLView].[PhasesBudgetRemaining] AS [PhasesBudgetRemaining], 
[TheSQLView].[PhasesOver] AS [PhasesOver]
FROM [dbo].[TheSQLView] AS [TheSQLView]) AS [Extent1]
    INNER JOIN (SELECT 
[TheSQLTable].[ID] AS [ID], 
[TheSQLTable].[IsCompleted] AS [IsCompleted], 
[TheSQLTable].[PctCompleted] AS [PctCompleted]
FROM [dbo].[TheSQLTable] AS [TheSQLTable]) AS [Extent2] ON [Extent1].[ID] = [Extent2].[ID]
)  AS [Project1]
ORDER BY [Project1].[ID] ASC

Answer 1

你的问题中有很少的信息。 生成的SQL很不错，但如果您还从SQL事件探查器发布了cpu +逻辑读取计数器，那就更好了。

但是，我会回答一下：查看索引视图（聚集索引不少）。 我强烈怀疑你的观点没有。 在这里找一些链接让你前往： https ： //stackoverflow.com/a/3986540/1736944

一个警告：如果您没有使用SQL Server企业版，那么您的查询必须包含“WITH（NOEXPAND）”提示。 只需创建第二个视图，从第一个视图中选择所有行，并在EF查询中引用第二个视图。 使用SQL事件探查器+查询计划确认您获得了合理的查询计划。