Indeks klastrowy nieużywany w instrukcji delete

13

Mam tabelę programu SQL Server zdefiniowaną w następujący sposób

CREATE TABLE [dbo].[Production_Detail]
(
    [Id] [bigint] NOT NULL DEFAULT (NEXT VALUE FOR [dbo].[Production_Detail_Seq]),
    [Meta_Data_ID] INT NOT NULL , 
    [Production_Detail_Time] DATETIME NOT NULL,
    [Production_Detail_Time_Local] DATETIME NOT NULL,
    [Production_Detail_Value] FLOAT NULL,
    [IntegratedDM] BIT NOT NULL DEFAULT 0,
    [DailyIntegratedDM] BIT NOT NULL DEFAULT 0,
    [InsertedDate] DateTime NOT NULL,
    [ModifiedDate] DateTime NOT NULL,  

    CONSTRAINT [PK_Production_Detail] PRIMARY KEY ([Id]), 

    CONSTRAINT [UK_Production_Detail] UNIQUE ([Meta_Data_Id], [Production_Detail_Time]),

    CONSTRAINT [FK_Production_Detail_To_Meta_Data] FOREIGN KEY ([Meta_Data_ID]) REFERENCES [Meta_Data]([Meta_Data_ID]) 
)
GO

CREATE NONCLUSTERED INDEX [IX_Production_Detail_Production_Detail_Time_Local]
ON [dbo].[Production_Detail] ([Production_Detail_Time_Local])
INCLUDE ([Meta_Data_ID], [Production_Detail_Time], [Production_Detail_Value])
GO

CREATE UNIQUE NONCLUSTERED INDEX [IX_Production_Detail_Meta_Data_ID_Production_Detail_Time] 
ON [dbo].[Production_Detail] ([Meta_Data_ID] ASC, [Production_Detail_Time] ASC)
GO

CREATE NONCLUSTERED INDEX [IX_Production_Detail_IntegratedDM_MetaDataId]
ON [dbo].[Production_Detail] ([IntegratedDM], [Meta_Data_ID])
INCLUDE ([Production_Detail_Time])
GO

Ta tabela zawiera dane w czasie rzeczywistym, więc rekordy są konsekwentnie wstawiane. Próbuję usunąć dane starsze niż 5 dni. Ale gdy działa usuwanie, mam kilka instrukcji insert, które rzucają impas.

Oto zapytanie dotyczące usuwania. #ToPurgeTabela zawiera identyfikator, który musi być usunięty. #ToPurgeTabela nie ma żadnych indeksów. Liczba wierszy może się różnić, ale w moim przypadku testowym miał ponad 3 miliony:

Declare @RowCount int;
set @RowCount = @@ROWCOUNT;

while @RowCount > 0
begin
    delete top(20000) pd
    from #ToPurge tp
    inner join [DataWarehouse].[dbo].[Production_Detail] pd on (tp.ID = pd.ID)

    set @RowCount = @@ROWCOUNT;
end

Oto plan wykonania z zapytania dotyczącego usuwania

wprowadź opis zdjęcia tutaj

<?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="1.2" Build="11.0.3128.0" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
  <BatchSequence>
    <Batch>
      <Statements>
        <StmtSimple StatementCompId="1" StatementEstRows="20000" StatementId="1" StatementOptmLevel="FULL" StatementSubTreeCost="34.7996" StatementText="   delete top(20000) pd&#xD;&#xA;  from #ToPurge tp&#xD;&#xA;  inner join [DataWarehouse].[dbo].[Production_Detail] pd on (tp.ID = pd.ID)" StatementType="DELETE" QueryHash="0xF7A9CF8E140CDB4E" QueryPlanHash="0x2CC61A780737A398" RetrievedFromCache="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 CachedPlanSize="88" CompileTime="65" CompileCPU="65" CompileMemory="592">
            <ThreadStat Branches="2" />
            <MemoryGrantInfo SerialRequiredMemory="1024" SerialDesiredMemory="477448" />
            <OptimizerHardwareDependentProperties EstimatedAvailableMemoryGrant="209715" EstimatedPagesCached="419430" EstimatedAvailableDegreeOfParallelism="4" />
            <RelOp AvgRowSize="9" EstimateCPU="0.08" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Sequence" NodeId="0" Parallel="false" PhysicalOp="Sequence" EstimatedTotalSubtreeCost="34.7996">
              <OutputList />
              <Sequence>
                <RelOp AvgRowSize="9" EstimateCPU="0.02" EstimateIO="0.458155" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Delete" NodeId="1" Parallel="false" PhysicalOp="Index Delete" EstimatedTotalSubtreeCost="8.56272">
                  <OutputList />
                  <Update WithUnorderedPrefetch="true" DMLRequestSort="false">
                    <Object Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Index="[UK_Production_Detail]" Alias="[pd]" IndexKind="NonClustered" />
                    <RelOp AvgRowSize="36" EstimateCPU="0.00182568" EstimateIO="0.00328238" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Eager Spool" NodeId="3" Parallel="false" PhysicalOp="Table Spool" EstimatedTotalSubtreeCost="8.08456">
                      <OutputList>
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Meta_Data_ID" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time_Local" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="IntegratedDM" />
                      </OutputList>
                      <Spool>
                        <RelOp AvgRowSize="36" EstimateCPU="0.02" EstimateIO="1.31642" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Delete" NodeId="4" Parallel="false" PhysicalOp="Clustered Index Delete" EstimatedTotalSubtreeCost="32.3067">
                          <OutputList>
                            <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                            <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Meta_Data_ID" />
                            <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time" />
                            <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time_Local" />
                            <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="IntegratedDM" />
                          </OutputList>
                          <Update WithUnorderedPrefetch="true" DMLRequestSort="false">
                            <Object Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Index="[PK_Production_Detail]" Alias="[pd]" IndexKind="Clustered" />
                            <RelOp AvgRowSize="15" EstimateCPU="0.002" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Top" NodeId="6" Parallel="false" PhysicalOp="Top" EstimatedTotalSubtreeCost="30.9703">
                              <OutputList>
                                <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                              </OutputList>
                              <Top RowCount="false" IsPercent="false" WithTies="false">
                                <TopExpression>
                                  <ScalarOperator ScalarString="(20000)">
                                    <Const ConstValue="(20000)" />
                                  </ScalarOperator>
                                </TopExpression>
                                <RelOp AvgRowSize="15" EstimateCPU="0.0392491" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Gather Streams" NodeId="7" Parallel="true" PhysicalOp="Parallelism" EstimatedTotalSubtreeCost="30.9683">
                                  <OutputList>
                                    <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                  </OutputList>
                                  <Parallelism>
                                    <RelOp AvgRowSize="15" EstimateCPU="276.841" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Right Semi Join" NodeId="8" Parallel="true" PhysicalOp="Hash Match" EstimatedTotalSubtreeCost="30.929">
                                      <OutputList>
                                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                      </OutputList>
                                      <MemoryFractions Input="1" Output="1" />
                                      <Hash>
                                        <DefinedValues />
                                        <HashKeysBuild>
                                          <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                        </HashKeysBuild>
                                        <HashKeysProbe>
                                          <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                        </HashKeysProbe>
                                        <ProbeResidual>
                                          <ScalarOperator ScalarString="[DataWarehouse].[dbo].[Production_Detail].[Id] as [pd].[Id]=[tempdb].[dbo].[#ToPurge].[Id] as [tp].[Id]">
                                            <Compare CompareOp="EQ">
                                              <ScalarOperator>
                                                <Identifier>
                                                  <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                                </Identifier>
                                              </ScalarOperator>
                                              <ScalarOperator>
                                                <Identifier>
                                                  <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                                </Identifier>
                                              </ScalarOperator>
                                            </Compare>
                                          </ScalarOperator>
                                        </ProbeResidual>
                                        <RelOp AvgRowSize="15" EstimateCPU="2.83429" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="3910180" LogicalOp="Bitmap Create" NodeId="9" Parallel="true" PhysicalOp="Bitmap" EstimatedTotalSubtreeCost="9.99726">
                                          <OutputList>
                                            <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                          </OutputList>
                                          <Bitmap>
                                            <DefinedValues>
                                              <DefinedValue>
                                                <ColumnReference Column="Bitmap1007" />
                                              </DefinedValue>
                                            </DefinedValues>
                                            <HashKeys>
                                              <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                            </HashKeys>
                                            <RelOp AvgRowSize="15" EstimateCPU="2.83429" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="3910180" LogicalOp="Repartition Streams" NodeId="10" Parallel="true" PhysicalOp="Parallelism" EstimatedTotalSubtreeCost="9.99726">
                                              <OutputList>
                                                <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                              </OutputList>
                                              <Parallelism PartitioningType="Hash">
                                                <PartitionColumns>
                                                  <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                                </PartitionColumns>
                                                <RelOp AvgRowSize="15" EstimateCPU="1.07532" EstimateIO="6.08765" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="3910180" LogicalOp="Table Scan" NodeId="11" Parallel="true" PhysicalOp="Table Scan" EstimatedTotalSubtreeCost="7.16297" TableCardinality="3910180">
                                                  <OutputList>
                                                    <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                                  </OutputList>
                                                  <TableScan Ordered="false" ForcedIndex="false" ForceScan="false" NoExpandHint="false">
                                                    <DefinedValues>
                                                      <DefinedValue>
                                                        <ColumnReference Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" Column="Id" />
                                                      </DefinedValue>
                                                    </DefinedValues>
                                                    <Object Database="[tempdb]" Schema="[dbo]" Table="[#ToPurge]" Alias="[tp]" IndexKind="Heap" />
                                                  </TableScan>
                                                </RelOp>
                                              </Parallelism>
                                            </RelOp>
                                          </Bitmap>
                                        </RelOp>
                                        <RelOp AvgRowSize="15" EstimateCPU="0.675882" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="902193" LogicalOp="Repartition Streams" NodeId="12" Parallel="true" PhysicalOp="Parallelism" EstimatedTotalSubtreeCost="3.17684">
                                          <OutputList>
                                            <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                          </OutputList>
                                          <Parallelism PartitioningType="Hash">
                                            <PartitionColumns>
                                              <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                            </PartitionColumns>
                                            <RelOp AvgRowSize="15" EstimateCPU="43.216" EstimateIO="391.867" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="902193" LogicalOp="Index Scan" NodeId="13" Parallel="true" PhysicalOp="Index Scan" EstimatedTotalSubtreeCost="2.50096" TableCardinality="157149000">
                                              <OutputList>
                                                <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                              </OutputList>
                                              <IndexScan Ordered="true" ScanDirection="FORWARD" ForcedIndex="false" ForceSeek="false" ForceScan="false" NoExpandHint="false" Storage="RowStore">
                                                <DefinedValues>
                                                  <DefinedValue>
                                                    <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                                  </DefinedValue>
                                                </DefinedValues>
                                                <Object Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Index="[UK_Production_Detail]" Alias="[pd]" IndexKind="NonClustered" />
                                                <Predicate>
                                                  <ScalarOperator ScalarString="PROBE([Bitmap1007],[DataWarehouse].[dbo].[Production_Detail].[Id] as [pd].[Id],N'[IN ROW]')">
                                                    <Intrinsic FunctionName="PROBE">
                                                      <ScalarOperator>
                                                        <Identifier>
                                                          <ColumnReference Column="Bitmap1007" />
                                                        </Identifier>
                                                      </ScalarOperator>
                                                      <ScalarOperator>
                                                        <Identifier>
                                                          <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                                                        </Identifier>
                                                      </ScalarOperator>
                                                      <ScalarOperator>
                                                        <Const ConstValue="N'[IN ROW]'" />
                                                      </ScalarOperator>
                                                    </Intrinsic>
                                                  </ScalarOperator>
                                                </Predicate>
                                              </IndexScan>
                                            </RelOp>
                                          </Parallelism>
                                        </RelOp>
                                      </Hash>
                                    </RelOp>
                                  </Parallelism>
                                </RelOp>
                              </Top>
                            </RelOp>
                          </Update>
                        </RelOp>
                      </Spool>
                    </RelOp>
                  </Update>
                </RelOp>
                <RelOp AvgRowSize="9" EstimateCPU="0.02" EstimateIO="0.906841" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Delete" NodeId="16" Parallel="false" PhysicalOp="Index Delete" EstimatedTotalSubtreeCost="9.0114">
                  <OutputList />
                  <Update WithUnorderedPrefetch="true" DMLRequestSort="false">
                    <Object Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Index="[IX_Production_Detail_Production_Detail_Time_Local]" Alias="[pd]" IndexKind="NonClustered" />
                    <RelOp AvgRowSize="36" EstimateCPU="0.00182568" EstimateIO="0.00328238" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Eager Spool" NodeId="18" Parallel="false" PhysicalOp="Table Spool" EstimatedTotalSubtreeCost="8.08456">
                      <OutputList>
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Meta_Data_ID" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time_Local" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="IntegratedDM" />
                      </OutputList>
                      <Spool PrimaryNodeId="3" />
                    </RelOp>
                  </Update>
                </RelOp>
                <RelOp AvgRowSize="9" EstimateCPU="0.02" EstimateIO="0.458164" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Delete" NodeId="19" Parallel="false" PhysicalOp="Index Delete" EstimatedTotalSubtreeCost="8.56272">
                  <OutputList />
                  <Update WithUnorderedPrefetch="true" DMLRequestSort="false">
                    <Object Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Index="[IX_Production_Detail_Meta_Data_ID_Production_Detail_Time]" Alias="[pd]" IndexKind="NonClustered" />
                    <RelOp AvgRowSize="36" EstimateCPU="0.00182568" EstimateIO="0.00328238" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Eager Spool" NodeId="21" Parallel="false" PhysicalOp="Table Spool" EstimatedTotalSubtreeCost="8.08456">
                      <OutputList>
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Meta_Data_ID" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time_Local" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="IntegratedDM" />
                      </OutputList>
                      <Spool PrimaryNodeId="3" />
                    </RelOp>
                  </Update>
                </RelOp>
                <RelOp AvgRowSize="9" EstimateCPU="0.02" EstimateIO="0.478182" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Delete" NodeId="22" Parallel="false" PhysicalOp="Index Delete" EstimatedTotalSubtreeCost="8.58274">
                  <OutputList />
                  <Update WithUnorderedPrefetch="true" DMLRequestSort="false">
                    <Object Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Index="[IX_Production_Detail_IntegratedDM_MetaDataId]" Alias="[pd]" IndexKind="NonClustered" />
                    <RelOp AvgRowSize="36" EstimateCPU="0.00182568" EstimateIO="0.00328238" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="20000" LogicalOp="Eager Spool" NodeId="24" Parallel="false" PhysicalOp="Table Spool" EstimatedTotalSubtreeCost="8.08456">
                      <OutputList>
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Id" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Meta_Data_ID" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="Production_Detail_Time_Local" />
                        <ColumnReference Database="[DataWarehouse]" Schema="[dbo]" Table="[Production_Detail]" Alias="[pd]" Column="IntegratedDM" />
                      </OutputList>
                      <Spool PrimaryNodeId="3" />
                    </RelOp>
                  </Update>
                </RelOp>
              </Sequence>
            </RelOp>
          </QueryPlan>
        </StmtSimple>
      </Statements>
    </Batch>
  </BatchSequence>
</ShowPlanXML>

Jak widać w planie wykonania, optymalizator nie korzysta z indeksu klastrowego podstawowego, ale zamiast tego używa klucza Unique, który nie zawiera pola Id. Myślę, że to jest powód, dla którego mam zakleszczenie, ponieważ musi zablokować więcej stron niż przy właściwym indeksie.

Próbuję dodać indeks nieklastrowany o identyfikatorze, a następnie używa go optymalizator.

CREATE UNIQUE NONCLUSTERED INDEX [NonClusteredIndex-20160617-104555] 
ON [dbo].[Production_Detail] ([Id] ASC)    
GO

Chciałbym wiedzieć, dlaczego optymalizator nie używa indeksu klastrowanego, ale używa indeksu nieklastrowanego?

sql-server  sql-server-2012  index  delete  clustered-index 
— tolrahC
źródło

Odpowiedzi:

10

Chciałbym wiedzieć, dlaczego optymalizator nie używa indeksu klastrowanego, ale używa indeksu nieklastrowanego?

Będzie to decyzja optymalizatora kosztowego. Szacuje się, że tańsze jest pełne skanowanie wąskiego indeksu.

Wygląda na to, że spodziewałeś się zagnieżdżonych pętli z szukaniem indeksu klastrowego?

Plan wykonania pokazuje, że tabela #ToPurgema 3,9 miliona wierszy.

Usunięcie zajmie 195 partii. Zakładając, że wszystkie wiersze #ToPurgesą unikalne i początkowo istnieją Production_Detaili że wiersze wyjściowe z #ToPurgesą w spójnej kolejności dla każdej partii (ignoruję równoległość), to każda kolejna partia zakończy wyszukiwanie wszystkich wierszy, które zostały już usunięte w poprzednim partie, zanim wreszcie dojdziemy do łaty wierszy, które nie zostały jeszcze przetworzone, to w sumie deleteproces wykona ponad jedną trzecią miliarda indeksów dla już usuniętych wierszy .

0 + 20,000 + 40,000 + ... + 3,880,000 = 378,300,000

Nie jest to logika wykorzystywana przez optymalizator oparty na kosztach (który obejmuje histogramy dwóch tabel i cel wiersza dla TOP 20000), ale pokazuje, że i tak nie jest to dobra strategia.

Możesz spróbować wykonać poniższe czynności, aby ograniczyć liczbę wyszukiwań do 20 000 na iterację i sprawdzić, czy otrzymujesz żądany plan. 

CREATE TABLE #ToPurge
  (
     [BatchId] [INT] NULL,
     [Id]      [BIGINT] NOT NULL,
     UNIQUE CLUSTERED([BatchId], [Id])
  );

/*Your insert statement to #ToPurge here*/

WITH CTE
     AS (SELECT *,
                1 + ( ROW_NUMBER() OVER (ORDER BY Id) / 20000 ) AS _BatchId
         FROM   #ToPurge)
UPDATE CTE
SET    [BatchId] = [_BatchId];

DECLARE @BatchCounter INT = 1;

WHILE @BatchCounter <= (SELECT MAX([BatchId])
                        FROM   #ToPurge)
  BEGIN
      DELETE pd
      FROM   #ToPurge tp
             INNER JOIN [DataWarehouse].[dbo].[Production_Detail] pd
               ON ( tp.ID = pd.ID )
      WHERE  tp.BatchId = @BatchCounter

      SET @BatchCounter+=1;
  END
— Martin Smith
źródło
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