Question

我们当前有一些客户，他们的查询需要很长时间才能从分区视图中获得结果。仔细观察后，我们发现了扫描每个表的执行计划，而不仅仅是具有相关数据的表。

为了隔离这种行为，我从https://technet.microsoft.com/en-us/library/ms190019(v=sql.105).aspx获取了分区视图示例并重新创建了我们的问题：

在这个例子中，我们有12个表（1998年的每个月）：

CREATE TABLE Jan1998sales
(
    OrderID INT,
    CustomerID INT NOT NULL,
    OrderDate DATETIME NULL CHECK(DATEPART(yy, OrderDate) = 1998),
    OrderMonth INT CHECK (OrderMonth = 1),
    DeliveryDate DATETIME NULL CHECK(DATEPART(MM, DeliveryDate) = 1),
    CONSTRAINT Jan1998sales_OrderIDMonth PRIMARY KEY (OrderID, OrderMonth)
)

我们正在查看如下视图：

CREATE VIEW Year1998Sales
AS
(
    SELECT * FROM Jan1998Sales
    UNION ALL
    SELECT * FROM Feb1998Sales
    UNION ALL
    SELECT * FROM Mar1998Sales
    UNION ALL
    [...]
    UNION ALL
    SELECT * FROM Dec1998Sales
)

现在我们有一个完全正常的查询（只扫描必要的表）：

SELECT * FROM Year1998Sales
WHERE (OrderMonth = 5 OR OrderMonth = 6) AND CustomerID = 64892

但如果我们使用参数进行过滤，它会突然扫描所有表格：

DECLARE @MonthA int = 5
DECLARE @MonthB int = 6

SELECT * FROM Year1998Sales
WHERE (OrderMonth = @MonthA OR OrderMonth = @MonthB) AND CustomerID = 64892

我解释这种行为的第一个猜测是，Microsoft SQL Server构建一次执行计划，扫描所有表，并在每次执行此查询时重复使用它，因此始终扫描所有表。

有谁知道我们如何让SQL Server只扫描必要的表并仍使用参数化过滤器？或者任何人都可以确认这是SQL Server执行计划构建器中的错误吗？

对于完整的代码，请看看这个SQL小提琴： http://sqlfiddle.com/#!6/e1f33/1

Answer 1

一般来说，OR谓词对SQL Server进行优化并生成可重用的缓存计划具有挑战性。

我使用OPTION(RECOMPILE)查询提示运行查询，实际执行计划显示不需要的分区视图成员表从计划中静态消除。不确定为什么sqlfiddle没有显示这个（它目前正在使用SQL 2014 RTM）但我观察到从2012年到2017年RC2的所有版本的SQL Server都安装了最新的服务包。

DECLARE @MonthA int = 5
DECLARE @MonthB int = 6;

SELECT *
FROM Year1998Sales
WHERE (OrderMonth = @MonthA OR OrderMonth = @MonthB) AND CustomerID = 64892
OPTION(RECOMPILE);

这是实际的执行计划XML（SQL Server 2017 RC2）：

<?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="1.6" Build="14.0.900.75" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
  <BatchSequence>
    <Batch>
      <Statements>
        <StmtSimple StatementCompId="3" StatementEstRows="2" StatementId="1" StatementOptmLevel="FULL" StatementOptmEarlyAbortReason="GoodEnoughPlanFound" CardinalityEstimationModelVersion="140" StatementSubTreeCost="0.00656736" StatementText="SELECT *&#xD;&#xA;FROM Year1998Sales&#xD;&#xA;WHERE (OrderMonth = @MonthA OR OrderMonth = @MonthB) AND CustomerID = 64892&#xD;&#xA;OPTION(RECOMPILE)" StatementType="SELECT" QueryHash="0xF9DB04D00D56A43D" QueryPlanHash="0x6171395FA7A2F92C" RetrievedFromCache="false" 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="1" CachedPlanSize="24" CompileTime="8" CompileCPU="8" CompileMemory="552">
            <MemoryGrantInfo SerialRequiredMemory="0" SerialDesiredMemory="0" />
            <OptimizerHardwareDependentProperties EstimatedAvailableMemoryGrant="419405" EstimatedPagesCached="104851" EstimatedAvailableDegreeOfParallelism="2" MaxCompileMemory="9985376" />
            <QueryTimeStats CpuTime="0" ElapsedTime="0" />
            <RelOp AvgRowSize="35" EstimateCPU="2E-07" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="2" LogicalOp="Concatenation" NodeId="0" Parallel="false" PhysicalOp="Concatenation" EstimatedTotalSubtreeCost="0.00656736">
              <OutputList>
                <ColumnReference Column="Union1014" />
                <ColumnReference Column="Union1015" />
                <ColumnReference Column="Union1016" />
                <ColumnReference Column="Union1017" />
                <ColumnReference Column="Union1018" />
              </OutputList>
              <RunTimeInformation>
                <RunTimeCountersPerThread Thread="0" ActualRows="0" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="0" ActualCPUms="0" />
              </RunTimeInformation>
              <Concat>
                <DefinedValues>
                  <DefinedValue>
                    <ColumnReference Column="Union1014" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderID" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderID" />
                  </DefinedValue>
                  <DefinedValue>
                    <ColumnReference Column="Union1015" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="CustomerID" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="CustomerID" />
                  </DefinedValue>
                  <DefinedValue>
                    <ColumnReference Column="Union1016" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderDate" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderDate" />
                  </DefinedValue>
                  <DefinedValue>
                    <ColumnReference Column="Union1017" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderMonth" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderMonth" />
                  </DefinedValue>
                  <DefinedValue>
                    <ColumnReference Column="Union1018" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="DeliveryDate" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="DeliveryDate" />
                  </DefinedValue>
                </DefinedValues>
                <RelOp AvgRowSize="35" EstimateCPU="0.0001581" EstimateIO="0.003125" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="1" EstimatedRowsRead="1" LogicalOp="Clustered Index Scan" NodeId="1" Parallel="false" PhysicalOp="Clustered Index Scan" EstimatedTotalSubtreeCost="0.0032831" TableCardinality="0">
                  <OutputList>
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderID" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="CustomerID" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderDate" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderMonth" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="DeliveryDate" />
                  </OutputList>
                  <RunTimeInformation>
                    <RunTimeCountersPerThread Thread="0" ActualRows="0" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="0" ActualCPUms="0" ActualScans="1" ActualLogicalReads="0" 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="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderID" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="CustomerID" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderDate" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="OrderMonth" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="DeliveryDate" />
                      </DefinedValue>
                    </DefinedValues>
                    <Object Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Index="[May1998sales_OrderIDMonth]" IndexKind="Clustered" Storage="RowStore" />
                    <Predicate>
                      <ScalarOperator ScalarString="[Repro].[dbo].[May1998sales].[CustomerID]=(64892)">
                        <Compare CompareOp="EQ">
                          <ScalarOperator>
                            <Identifier>
                              <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[May1998sales]" Column="CustomerID" />
                            </Identifier>
                          </ScalarOperator>
                          <ScalarOperator>
                            <Const ConstValue="(64892)" />
                          </ScalarOperator>
                        </Compare>
                      </ScalarOperator>
                    </Predicate>
                  </IndexScan>
                </RelOp>
                <RelOp AvgRowSize="35" EstimateCPU="0.0001581" EstimateIO="0.003125" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="1" EstimatedRowsRead="1" LogicalOp="Clustered Index Scan" NodeId="2" Parallel="false" PhysicalOp="Clustered Index Scan" EstimatedTotalSubtreeCost="0.0032831" TableCardinality="0">
                  <OutputList>
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderID" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="CustomerID" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderDate" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderMonth" />
                    <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="DeliveryDate" />
                  </OutputList>
                  <RunTimeInformation>
                    <RunTimeCountersPerThread Thread="0" ActualRows="0" Batches="0" ActualEndOfScans="1" ActualExecutions="1" ActualExecutionMode="Row" ActualElapsedms="0" ActualCPUms="0" ActualScans="1" ActualLogicalReads="0" 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="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderID" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="CustomerID" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderDate" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="OrderMonth" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="DeliveryDate" />
                      </DefinedValue>
                    </DefinedValues>
                    <Object Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Index="[Jun1998sales_OrderIDMonth]" IndexKind="Clustered" Storage="RowStore" />
                    <Predicate>
                      <ScalarOperator ScalarString="[Repro].[dbo].[Jun1998sales].[CustomerID]=(64892)">
                        <Compare CompareOp="EQ">
                          <ScalarOperator>
                            <Identifier>
                              <ColumnReference Database="[Repro]" Schema="[dbo]" Table="[Jun1998sales]" Column="CustomerID" />
                            </Identifier>
                          </ScalarOperator>
                          <ScalarOperator>
                            <Const ConstValue="(64892)" />
                          </ScalarOperator>
                        </Compare>
                      </ScalarOperator>
                    </Predicate>
                  </IndexScan>
                </RelOp>
              </Concat>
            </RelOp>
          </QueryPlan>
        </StmtSimple>
      </Statements>
    </Batch>
  </BatchSequence>
</ShowPlanXML>

Partitioned-View不使用参数

1 个答案: