参数化的 OFFSET FETCH NEXT 查询（EF Core）的性能降低了 10 倍答案

【问题标题】：Parameterised OFFSET FETCH NEXT query (EF Core) has 10x slower performance参数化的 OFFSET FETCH NEXT 查询（EF Core）的性能降低了 10 倍
【发布时间】：2018-09-26 07:18:12
【问题描述】：

我正在通过（由 Entity Framework Core 生成）Microsoft SQL Server Management Studio 对具有约 46,000 行的 SQL Azure 数据库表运行以下查询，这需要约 5 秒

DECLARE @__TypedProperty_0 as int = 20
DECLARE @__TypedProperty_1 as int = 20

SELECT [dto].[Id], [dto].[Forename], [dto].[Surname], [dto].[AzureId], [dto].[Email]
 FROM [Associates] AS [dto]
 ORDER BY [dto].[Forename], [dto].[Id]
 OFFSET @__TypedProperty_0 ROWS FETCH NEXT @__TypedProperty_1 ROWS ONLY

这会产生以下执行计划：

相同的查询，内联如下参数，运行时间为 500 毫秒 - 快 10 倍！

SELECT [dto].[Id], [dto].[Forename], [dto].[Surname], [dto].[AzureId], [dto].[Email]
 FROM [Associates] AS [dto]
 ORDER BY [dto].[Forename], [dto].[Id]
 OFFSET 20 ROWS FETCH NEXT 20 ROWS ONLY

但会产生几乎相同的执行计划：

此代码由 EntityFramework Core 生成，因此我无法控制它。我的问题是：

为什么这些看似相同的执行计划会导致截然不同的性能结果
如何提高此查询的参数化版本的性能？

这个表基本上是这样创建的（为了简洁省略了一些列）：

CREATE TABLE [dbo].[Associates](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [AzureId] [nvarchar](max) NULL,
    [Email] [nvarchar](max) NULL,
    [Forename] [nvarchar](max) NULL,
    [Surname] [nvarchar](max) NULL,
 CONSTRAINT [PK_Associates] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
)

编辑：

参数化计划：

<?xml version="1.0" encoding="utf-16"?>
<ShowPlanXML xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Version="1.520" Build="15.0.300.379" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
  <BatchSequence>
    <Batch>
      <Statements>
        <StmtSimple StatementCompId="3" StatementEstRows="100" StatementId="2" StatementOptmLevel="FULL" CardinalityEstimationModelVersion="130" StatementSubTreeCost="5.37918" StatementText="SELECT [dto].[Id], [dto].[Forename], [dto].[Surname], [dto].[AzureId], [dto].[Email]&#xD; FROM [Associates] AS [dto]&#xD; ORDER BY [dto].[Forename], [dto].[Id]&#xD; OFFSET @__TypedProperty_0 ROWS FETCH NEXT @__TypedProperty_1 ROWS ONLY" StatementType="SELECT" QueryHash="0x0DE3D0FE5886DC7C" QueryPlanHash="0xF19DA08DF72AADE7" RetrievedFromCache="true" StatementSqlHandle="0x09005281339FAE104036AAAECEB2DCBF22BA0000000000000000000000000000000000000000000000000000" DatabaseContextSettingsId="4" ParentObjectId="0" StatementParameterizationType="0" SecurityPolicyApplied="false">
          <StatementSetOptions ANSI_NULLS="true" ANSI_PADDING="true" ANSI_WARNINGS="true" ARITHABORT="true" CONCAT_NULL_YIELDS_NULL="true" NUMERIC_ROUNDABORT="false" QUOTED_IDENTIFIER="true" />
          <QueryPlan DegreeOfParallelism="0" NonParallelPlanReason="EstimatedDOPIsOne" MemoryGrant="242880" CachedPlanSize="24" CompileTime="1" CompileCPU="1" CompileMemory="192">
            <Warnings>
              <MemoryGrantWarning GrantWarningKind="Excessive Grant" RequestedMemory="242880" GrantedMemory="242880" MaxUsedMemory="8824" />
            </Warnings>
            <MemoryGrantInfo SerialRequiredMemory="512" SerialDesiredMemory="909960" RequiredMemory="512" DesiredMemory="909960" RequestedMemory="242880" GrantWaitTime="0" GrantedMemory="242880" MaxUsedMemory="8824" MaxQueryMemory="242888" />
            <OptimizerHardwareDependentProperties EstimatedAvailableMemoryGrant="17616030" EstimatedPagesCached="1101001" EstimatedAvailableDegreeOfParallelism="1" MaxCompileMemory="849240" />
            <WaitStats>
              <Wait WaitType="SOS_SCHEDULER_YIELD" WaitTimeMs="4860" WaitCount="63" />
              <Wait WaitType="RESOURCE_GOVERNOR_IDLE" WaitTimeMs="2622" WaitCount="190" />
            </WaitStats>
            <QueryTimeStats CpuTime="293" ElapsedTime="5152" />
            <RelOp AvgRowSize="16117" EstimateCPU="1E-05" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="100" LogicalOp="Top" NodeId="0" Parallel="false" PhysicalOp="Top" EstimatedTotalSubtreeCost="5.37918">
              <OutputList>
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
              </OutputList>
              <RunTimeInformation>
                <RunTimeCountersPerThread Thread="0" ActualRows="20" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="5151" ActualCPUms="292" />
              </RunTimeInformation>
              <Top RowCount="false" IsPercent="false" WithTies="false">
                <OffsetExpression>
                  <ScalarOperator ScalarString="CONVERT_IMPLICIT(bigint,[@__TypedProperty_0],0)">
                    <Identifier>
                      <ColumnReference Column="ConstExpr1002">
                        <ScalarOperator>
                          <Convert DataType="bigint" Style="0" Implicit="true">
                            <ScalarOperator>
                              <Identifier>
                                <ColumnReference Column="@__TypedProperty_0" />
                              </Identifier>
                            </ScalarOperator>
                          </Convert>
                        </ScalarOperator>
                      </ColumnReference>
                    </Identifier>
                  </ScalarOperator>
                </OffsetExpression>
                <TopExpression>
                  <ScalarOperator ScalarString="CONVERT_IMPLICIT(bigint,[@__TypedProperty_1],0)">
                    <Identifier>
                      <ColumnReference Column="ConstExpr1001">
                        <ScalarOperator>
                          <Convert DataType="bigint" Style="0" Implicit="true">
                            <ScalarOperator>
                              <Identifier>
                                <ColumnReference Column="@__TypedProperty_1" />
                              </Identifier>
                            </ScalarOperator>
                          </Convert>
                        </ScalarOperator>
                      </ColumnReference>
                    </Identifier>
                  </ScalarOperator>
                </TopExpression>
                <RelOp AvgRowSize="16117" EstimateCPU="3.27909" EstimateIO="0.0112613" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="100" LogicalOp="Sort" NodeId="1" Parallel="false" PhysicalOp="Sort" EstimatedTotalSubtreeCost="5.37917">
                  <OutputList>
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
                  </OutputList>
                  <MemoryFractions Input="1" Output="1" />
                  <RunTimeInformation>
                    <RunTimeCountersPerThread Thread="0" ActualRebinds="1" ActualRewinds="0" ActualRows="40" Batches="0" ActualEndOfScans="0" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="5151" ActualCPUms="292" ActualScans="0" ActualLogicalReads="0" ActualPhysicalReads="0" ActualReadAheads="0" ActualLobLogicalReads="0" ActualLobPhysicalReads="0" ActualLobReadAheads="0" InputMemoryGrant="242880" OutputMemoryGrant="242496" UsedMemoryGrant="8824" />
                  </RunTimeInformation>
                  <Sort Distinct="false">
                    <OrderBy>
                      <OrderByColumn Ascending="true">
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                      </OrderByColumn>
                      <OrderByColumn Ascending="true">
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                      </OrderByColumn>
                    </OrderBy>
                    <RelOp AvgRowSize="16117" EstimateCPU="0.050878" EstimateIO="2.03794" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="46110" EstimatedRowsRead="46110" LogicalOp="Clustered Index Scan" NodeId="2" Parallel="false" PhysicalOp="Clustered Index Scan" EstimatedTotalSubtreeCost="2.08882" TableCardinality="46110">
                      <OutputList>
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
                      </OutputList>
                      <RunTimeInformation>
                        <RunTimeCountersPerThread Thread="0" ActualRows="46110" ActualRowsRead="46110" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="859" ActualCPUms="33" ActualScans="1" ActualLogicalReads="2759" ActualPhysicalReads="0" ActualReadAheads="0" ActualLobLogicalReads="0" ActualLobPhysicalReads="0" ActualLobReadAheads="0" />
                      </RunTimeInformation>
                      <IndexScan Ordered="false" ForcedIndex="false" ForceScan="false" NoExpandHint="false" Storage="RowStore">
                        <DefinedValues>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
                          </DefinedValue>
                        </DefinedValues>
                        <Object Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Index="[PK_Associates]" Alias="[dto]" IndexKind="Clustered" Storage="RowStore" />
                      </IndexScan>
                    </RelOp>
                  </Sort>
                </RelOp>
              </Top>
            </RelOp>
            <ParameterList>
              <ColumnReference Column="@__TypedProperty_0" ParameterDataType="int" ParameterRuntimeValue="(20)" />
              <ColumnReference Column="@__TypedProperty_1" ParameterDataType="int" ParameterRuntimeValue="(20)" />
            </ParameterList>
          </QueryPlan>
        </StmtSimple>
      </Statements>
    </Batch>
  </BatchSequence>
</ShowPlanXML>

非参数化计划：

<?xml version="1.0" encoding="utf-16"?>
<ShowPlanXML xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Version="1.520" Build="15.0.300.379" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
  <BatchSequence>
    <Batch>
      <Statements>
        <StmtSimple StatementCompId="1" StatementEstRows="20" StatementId="2" StatementOptmLevel="FULL" CardinalityEstimationModelVersion="130" StatementSubTreeCost="5.37917" StatementText="SELECT [dto].[Id], [dto].[Forename], [dto].[Surname], [dto].[AzureId], [dto].[Email]&#xD; FROM [Associates] AS [dto]&#xD; ORDER BY [dto].[Forename], [dto].[Id]&#xD; OFFSET 20 ROWS FETCH NEXT 20 ROWS ONLY" StatementType="SELECT" QueryHash="0x0DE3D0FE5886DC7C" QueryPlanHash="0x320ECFD7D3D25A6E" RetrievedFromCache="true" StatementSqlHandle="0x0900910E3823662F71FB79B11C319338FB890000000000000000000000000000000000000000000000000000" DatabaseContextSettingsId="4" ParentObjectId="0" StatementParameterizationType="0" SecurityPolicyApplied="false">
          <StatementSetOptions ANSI_NULLS="true" ANSI_PADDING="true" ANSI_WARNINGS="true" ARITHABORT="true" CONCAT_NULL_YIELDS_NULL="true" NUMERIC_ROUNDABORT="false" QUOTED_IDENTIFIER="true" />
          <QueryPlan DegreeOfParallelism="0" NonParallelPlanReason="EstimatedDOPIsOne" MemoryGrant="1024" CachedPlanSize="24" CompileTime="1" CompileCPU="1" CompileMemory="168">
            <MemoryGrantInfo SerialRequiredMemory="336" SerialDesiredMemory="352" RequiredMemory="336" DesiredMemory="352" RequestedMemory="1024" GrantWaitTime="0" GrantedMemory="1024" MaxUsedMemory="336" MaxQueryMemory="243624" />
            <OptimizerHardwareDependentProperties EstimatedAvailableMemoryGrant="17616030" EstimatedPagesCached="1101001" EstimatedAvailableDegreeOfParallelism="1" MaxCompileMemory="848432" />
            <WaitStats>
              <Wait WaitType="SOS_SCHEDULER_YIELD" WaitTimeMs="1713" WaitCount="23" />
              <Wait WaitType="RESOURCE_GOVERNOR_IDLE" WaitTimeMs="1130" WaitCount="83" />
            </WaitStats>
            <QueryTimeStats CpuTime="96" ElapsedTime="1808" />
            <RelOp AvgRowSize="16117" EstimateCPU="4E-06" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20" LogicalOp="Top" NodeId="0" Parallel="false" PhysicalOp="Top" EstimatedTotalSubtreeCost="5.37917">
              <OutputList>
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
              </OutputList>
              <RunTimeInformation>
                <RunTimeCountersPerThread Thread="0" ActualRows="20" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="1808" ActualCPUms="95" />
              </RunTimeInformation>
              <Top RowCount="false" IsPercent="false" WithTies="false">
                <OffsetExpression>
                  <ScalarOperator ScalarString="(20)">
                    <Const ConstValue="(20)" />
                  </ScalarOperator>
                </OffsetExpression>
                <TopExpression>
                  <ScalarOperator ScalarString="(20)">
                    <Const ConstValue="(20)" />
                  </ScalarOperator>
                </TopExpression>
                <RelOp AvgRowSize="16117" EstimateCPU="3.27909" EstimateIO="0.0112613" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="40" LogicalOp="TopN Sort" NodeId="1" Parallel="false" PhysicalOp="Sort" EstimatedTotalSubtreeCost="5.37917">
                  <OutputList>
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                    <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
                  </OutputList>
                  <MemoryFractions Input="1" Output="1" />
                  <RunTimeInformation>
                    <RunTimeCountersPerThread Thread="0" ActualRebinds="1" ActualRewinds="0" ActualRows="40" Batches="0" ActualEndOfScans="0" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="1808" ActualCPUms="95" ActualScans="0" ActualLogicalReads="0" ActualPhysicalReads="0" ActualReadAheads="0" ActualLobLogicalReads="0" ActualLobPhysicalReads="0" ActualLobReadAheads="0" InputMemoryGrant="1024" OutputMemoryGrant="1024" UsedMemoryGrant="336" />
                  </RunTimeInformation>
                  <TopSort Distinct="false" Rows="40">
                    <OrderBy>
                      <OrderByColumn Ascending="true">
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                      </OrderByColumn>
                      <OrderByColumn Ascending="true">
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                      </OrderByColumn>
                    </OrderBy>
                    <RelOp AvgRowSize="16117" EstimateCPU="0.050878" EstimateIO="2.03794" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="46110" EstimatedRowsRead="46110" LogicalOp="Clustered Index Scan" NodeId="2" Parallel="false" PhysicalOp="Clustered Index Scan" EstimatedTotalSubtreeCost="2.08882" TableCardinality="46110">
                      <OutputList>
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                        <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
                      </OutputList>
                      <RunTimeInformation>
                        <RunTimeCountersPerThread Thread="0" ActualRows="46110" ActualRowsRead="46110" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="1009" ActualCPUms="31" ActualScans="1" ActualLogicalReads="2759" ActualPhysicalReads="0" ActualReadAheads="0" ActualLobLogicalReads="0" ActualLobPhysicalReads="0" ActualLobReadAheads="0" />
                      </RunTimeInformation>
                      <IndexScan Ordered="false" ForcedIndex="false" ForceScan="false" NoExpandHint="false" Storage="RowStore">
                        <DefinedValues>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Id" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="AzureId" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Email" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Forename" />
                          </DefinedValue>
                          <DefinedValue>
                            <ColumnReference Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Alias="[dto]" Column="Surname" />
                          </DefinedValue>
                        </DefinedValues>
                        <Object Database="[MomentaUAT]" Schema="[dbo]" Table="[Associates]" Index="[PK_Associates]" Alias="[dto]" IndexKind="Clustered" Storage="RowStore" />
                      </IndexScan>
                    </RelOp>
                  </TopSort>
                </RelOp>
              </Top>
            </RelOp>
          </QueryPlan>
        </StmtSimple>
      </Statements>
    </Batch>
  </BatchSequence>
</ShowPlanXML>

【问题讨论】：

它们看起来相同，但是否它们相同？仔细查看每个计划中的行估计。或者更好的是，paste the plans。最后一步的感叹号很能说明问题！它很可能会警告您溢出。
顺便说一句，一般来说，OFFSET 20 可以快速制作，这一切都很好——但你总是会通过20 吗？试试OFFSET 43000，我想你会发现无论有没有参数化，它都会受到同样的伤害。如果您只专注于“尽可能快地做到这一点”，您可能会找错树。
@JeroenMostert 我已经用 xml 执行计划更新了我的问题。你实际上提出了一个很好的观点，当这样做时有趣的是内联参数版本需要更长的时间 - 6 秒，但参数化版本仍然需要 6 秒
@HenryIng-Simmons：你能尝试消除 EF 生成代码中的数据类型不匹配吗` `
我将从按列排序的索引开始

标签： sql azure-sql-database entity-framework-core

【解决方案1】：

请添加一个支持 ORDER BY ([dto].[Forename], [dto].[Id]) 并涵盖 SELECT 子句中所有列的索引。

CREATE NONCLUSTERED INDEX IX_Associates_Forename_ID  
ON Associates (Forename, Id)  
INCLUDE (Surname, AzureId, Email);

正如您在计划中看到的那样，在没有适当索引的情况下进行分页会引发扫描或键查找，这就是性能不佳的原因。

【讨论】：

即使使用完全覆盖的索引，分页也会被扫描——这正是野兽的本性。索引不存储行偏移量。（此外，将您已经索引的列放在 INCLUDE 中是不合法的，如果合法，无论如何都会浪费空间。）索引仍然有助于减少 I/O 并消除排序，当然，但它不会将分页减少到搜索。
按照您的建议在所有列上添加索引对于我的特定问题似乎有点笨拙。
@Jeroen sqlperformance.com/2015/01/t-sql-queries/…
我在该页面上没有看到任何与我所说的相矛盾的内容。尽管确实可以通过更多技巧来优化分页，但您的答案不是讨论这些。（顺便说一句，修复语句中的错误很容易——只需从 INCLUDE 中删除 Id 和 Forename。）
我没有说没有影响。我说过没有索引会减少分页到寻找。当您说添加索引可能会有所帮助时，我的论点并不是您错了-我的论点是，将其表述为“在没有适当索引的情况下进行分页会引发扫描”是误导性的，因为进行分页 with正确的索引仍将涉及扫描！（您可以在该页面上的每个执行计划中清楚地看到这一点——也许您的意思是“表扫描”。）