sql-server - 为什么这次加入需要这么长时间？

Question

我在数据库服务器上运行以下查询，但运行大约需要 30 秒，我无法弄清楚这是为什么。

SELECT *
FROM [dbo].[PackageInstance] AS packInst
  INNER JOIN [dbo].[PackageDefinition] AS packageDef 
    ON packInst.[PackageDefinitionID] = packageDef.[PackageDefinitionID]
  LEFT OUTER JOIN [dbo].[PackageInstanceContextDef] AS contextDef 
   ON packInst.[PackageInstanceID] = contextDef.[PackageInstanceID]

这产生了以下执行计划，对我来说看起来不错......所以我不明白为什么要花这么多时间来执行，而结果数据只有 100,000 条记录(这应该是在SQL Server 的停放)。

有什么想法可能导致这么长的执行时间吗？

我查看了 Profiler 中的查询，看看其中的统计信息，如下所示:

CPU - 4711
Reads - 744453
Writes - 9
Duration - 26329

以下是表定义:

CREATE TABLE [dbo].[PackageDefinition](
    [PackageDefinitionID] [int] IDENTITY(1,1) NOT NULL,
    [ts] [timestamp] NOT NULL,
    [ProgramID] [int] NULL,
    [VendorID] [int] NULL,
    [PackageExecutionTypeID] [int] NULL,
    [PackageDefinitionStatusID] [int] NOT NULL,
    [IsInternal] [bit] NOT NULL,
    [Name] [dbo].[D_Name] NOT NULL,
    [Description] [dbo].[D_Description] NOT NULL,
    [CreatedDate] [datetime] NOT NULL,
    [PublishedDate] [datetime] NULL,
    [OwnerUserGuid] [uniqueidentifier] NOT NULL,
    [ProcessDefinitionMainID] [int] NULL,
    [KeyInfoHtml] [nvarchar](max) NULL,
    [DescriptionHtml] [nvarchar](max) NULL,
    [WhatToExpectHtml] [nvarchar](max) NULL,
    [BestPracticesHtml] [nvarchar](max) NULL,
    [RecommendedJourneysHtml] [nvarchar](max) NULL,
    [RequiresSLAAgreement] [bit] NOT NULL,
    [SLAFileAssetID] [int] NULL,
    [ImageDataID] [int] NULL,
    [VideoHtml] [nvarchar](max) NULL,
    [VideoAssetID] [int] NULL,
    [UseMapCosts] [bit] NOT NULL,
    [CostMin] [money] NOT NULL,
    [CostMax] [money] NOT NULL,
    [LandingPageVisitCount] [int] NOT NULL,
    [IsDeleted] [dbo].[D_IsDeleted] NOT NULL,
    [CreatedByUserGuid] [uniqueidentifier] NOT NULL,
    [OrderHtml] [nvarchar](max) NULL,
 CONSTRAINT [PK_PackageDefinition] PRIMARY KEY CLUSTERED 
(
    [PackageDefinitionID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE TABLE [dbo].[PackageInstance](
    [PackageInstanceID] [int] IDENTITY(1,1) NOT NULL,
    [ts] [timestamp] NOT NULL,
    [PackageDefinitionID] [int] NOT NULL,
    [PackageStatusID] [int] NOT NULL,
    [Name] [dbo].[D_Description] NOT NULL,
    [CampaignID] [int] NULL,
    [MarketingPlanID] [int] NULL,
    [CountryID] [int] NULL,
    [DateEntered] [datetime] NULL,
    [DateExecuted] [datetime] NULL,
    [ProcessID] [int] NULL,
    [OrderedByUserGuid] [uniqueidentifier] NULL,
    [RequestedByUserGuid] [uniqueidentifier] NULL,
    [SLAEndDate] [datetime] NULL,
 CONSTRAINT [PK_PackageInstance] PRIMARY KEY CLUSTERED 
(
    [PackageInstanceID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE TABLE [dbo].[PackageInstanceContextDef](
    [PackageInstanceContextDefID] [int] IDENTITY(1,1) NOT NULL,
    [ts] [timestamp] NOT NULL,
    [PackageInstanceID] [int] NOT NULL,
    [ContextObjectDefID] [int] NOT NULL,
    [EnteredFieldValue] [varchar](max) NULL,
    [SelectedListValueID] [int] NULL,
    [AssetIdsString] [nvarchar](max) NULL,
    [SelectedListValueIdsString] [nvarchar](max) NULL,
    [ContextObjectFieldName] [nvarchar](30) NOT NULL,
 CONSTRAINT [PK_PackageInstanceContextDef] PRIMARY KEY CLUSTERED 
(
    [PackageInstanceContextDefID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

Answer 1

删除SELECT *中的*

它将始终扫描，因为您要求所有列。你有聚集索引吗？