SQL Server在第一次运行时快速查询，然后与其他生产数据一起查询速度极慢

Question

我有一个需要几分钟才能返回的查询。一旦它加载到RAM中就没问题，但是当我将参数更改为超出缓存中的参数时，一般性能很糟糕。 thing中约有1m行，location中有200k行。两个表都有索引和键。另外，两个查询（来自事物和位置）返回<1秒，但是当我进行连接（在FK上）时，它需要超过一分钟。

查询：

SELECT tip.id
    ,tip.NAME
    ,tip.location
    ,tip.time_start
    ,tip.time_end
    ,tip.is_meetup
    ,tip.utc_offset
    ,tip.type
    ,locations.NAME AS location_name
    ,locations.lat
    ,locations.long
FROM locations
INNER JOIN thing ON locations.id = thing.location
WHERE latitude BETWEEN 37.631281363768117
        AND 37.921136436231883
    AND longitude BETWEEN - 122.60055304642543
        AND - 122.23383795357458
    AND startTime BETWEEN 1373869967
        AND 1389869967

执行计划：

<?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="1.2" Build="11.0.3393.0" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
  <BatchSequence>
    <Batch>
      <Statements>
        <StmtSimple StatementCompId="1" StatementEstRows="268.558" StatementId="1" StatementOptmLevel="FULL" StatementSubTreeCost="2.04298" StatementText="SELECT t.id, t.name, t.location, t.time_start, t.time_end, t.is_meetup, t.utc_offset, t.type,&#xD;&#xA;locations.name AS location_name,&#xD;&#xA;locations.latitude AS latitude, locations.longitude AS longitude&#xD;&#xA;FROM locations &#xD;&#xA;INNER JOIN Thing AS t&#xD;&#xA;ON locations.id = t.location &#xD;&#xA;WHERE latitude BETWEEN 32.631281363768117 AND 33.921136436231883&#xD;&#xA;AND longitude BETWEEN -118.60055304642543 AND -116.23383795357458&#xD;&#xA;AND time_start BETWEEN 1390869967 AND 1391869967&#xD;&#xA;" StatementType="SELECT" QueryHash="0x545542B8298CBC85" QueryPlanHash="0xA2BF90229E96DA92" RetrievedFromCache="true">
          <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="40" CompileTime="11" CompileCPU="11" CompileMemory="464">
            <MemoryGrantInfo SerialRequiredMemory="0" SerialDesiredMemory="0" />
            <OptimizerHardwareDependentProperties EstimatedAvailableMemoryGrant="524288" EstimatedPagesCached="131072" EstimatedAvailableDegreeOfParallelism="2" />
            <RelOp AvgRowSize="4342" EstimateCPU="0.00243192" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="268.558" LogicalOp="Inner Join" NodeId="0" Parallel="false" PhysicalOp="Nested Loops" EstimatedTotalSubtreeCost="2.04298">
              <OutputList>
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="name" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="latitude" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="id" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="name" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="location" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_start" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_end" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="is_meetup" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="utc_offset" />
                <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="type" />
              </OutputList>
              <RunTimeInformation>
                <RunTimeCountersPerThread Thread="0" ActualRows="12" ActualEndOfScans="1" ActualExecutions="1" />
              </RunTimeInformation>
              <NestedLoops Optimized="false" WithUnorderedPrefetch="true">
                <OuterReferences>
                  <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="id" />
                  <ColumnReference Column="Expr1005" />
                </OuterReferences>
                <RelOp AvgRowSize="4059" EstimateCPU="0.016229" EstimateIO="0.10831" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="581.799" LogicalOp="Index Seek" NodeId="2" Parallel="false" PhysicalOp="Index Seek" EstimatedTotalSubtreeCost="0.124539" TableCardinality="255461">
                  <OutputList>
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="name" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="latitude" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="id" />
                  </OutputList>
                  <RunTimeInformation>
                    <RunTimeCountersPerThread Thread="0" ActualRows="5487" ActualEndOfScans="1" ActualExecutions="1" />
                  </RunTimeInformation>
                  <IndexScan Ordered="true" ScanDirection="FORWARD" ForcedIndex="false" ForceSeek="false" ForceScan="false" NoExpandHint="false" Storage="RowStore">
                    <DefinedValues>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="name" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="latitude" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="id" />
                      </DefinedValue>
                    </DefinedValues>
                    <Object Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Index="[IX_locations]" IndexKind="NonClustered" />
                    <SeekPredicates>
                      <SeekPredicateNew>
                        <SeekKeys>
                          <StartRange ScanType="GE">
                            <RangeColumns>
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="latitude" />
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                            </RangeColumns>
                            <RangeExpressions>
                              <ScalarOperator ScalarString="(3.263128136376812e+001)">
                                <Const ConstValue="(3.263128136376812e+001)" />
                              </ScalarOperator>
                              <ScalarOperator ScalarString="(-1.186005530464255e+002)">
                                <Const ConstValue="(-1.186005530464255e+002)" />
                              </ScalarOperator>
                            </RangeExpressions>
                          </StartRange>
                          <EndRange ScanType="LE">
                            <RangeColumns>
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="latitude" />
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                            </RangeColumns>
                            <RangeExpressions>
                              <ScalarOperator ScalarString="(3.392113643623188e+001)">
                                <Const ConstValue="(3.392113643623188e+001)" />
                              </ScalarOperator>
                              <ScalarOperator ScalarString="(-1.162338379535746e+002)">
                                <Const ConstValue="(-1.162338379535746e+002)" />
                              </ScalarOperator>
                            </RangeExpressions>
                          </EndRange>
                        </SeekKeys>
                      </SeekPredicateNew>
                    </SeekPredicates>
                    <Predicate>
                      <ScalarOperator ScalarString="[ThingDB].[dbo].[locations].[longitude]&gt;=(-1.186005530464255e+002) AND [ThingDB].[dbo].[locations].[longitude]&lt;=(-1.162338379535746e+002)">
                        <Logical Operation="AND">
                          <ScalarOperator>
                            <Compare CompareOp="GE">
                              <ScalarOperator>
                                <Identifier>
                                  <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                                </Identifier>
                              </ScalarOperator>
                              <ScalarOperator>
                                <Const ConstValue="(-1.186005530464255e+002)" />
                              </ScalarOperator>
                            </Compare>
                          </ScalarOperator>
                          <ScalarOperator>
                            <Compare CompareOp="LE">
                              <ScalarOperator>
                                <Identifier>
                                  <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="longitude" />
                                </Identifier>
                              </ScalarOperator>
                              <ScalarOperator>
                                <Const ConstValue="(-1.162338379535746e+002)" />
                              </ScalarOperator>
                            </Compare>
                          </ScalarOperator>
                        </Logical>
                      </ScalarOperator>
                    </Predicate>
                  </IndexScan>
                </RelOp>
                <RelOp AvgRowSize="299" EstimateCPU="0.0001581" EstimateIO="0.003125" EstimateRebinds="580.799" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="1" LogicalOp="Index Seek" NodeId="3" Parallel="false" PhysicalOp="Index Seek" EstimatedTotalSubtreeCost="1.90315" TableCardinality="767469">
                  <OutputList>
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="id" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="name" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="location" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_start" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_end" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="is_meetup" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="utc_offset" />
                    <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="type" />
                  </OutputList>
                  <RunTimeInformation>
                    <RunTimeCountersPerThread Thread="0" ActualRows="12" ActualEndOfScans="5487" ActualExecutions="5487" />
                  </RunTimeInformation>
                  <IndexScan Ordered="true" ScanDirection="FORWARD" ForcedIndex="false" ForceSeek="false" ForceScan="false" NoExpandHint="false" Storage="RowStore">
                    <DefinedValues>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="id" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="name" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="location" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_start" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_end" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="is_meetup" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="utc_offset" />
                      </DefinedValue>
                      <DefinedValue>
                        <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="type" />
                      </DefinedValue>
                    </DefinedValues>
                    <Object Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Index="[IX_Thing]" Alias="[t]" IndexKind="NonClustered" />
                    <SeekPredicates>
                      <SeekPredicateNew>
                        <SeekKeys>
                          <Prefix ScanType="EQ">
                            <RangeColumns>
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="location" />
                            </RangeColumns>
                            <RangeExpressions>
                              <ScalarOperator ScalarString="[ThingDB].[dbo].[locations].[id]">
                                <Identifier>
                                  <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[locations]" Column="id" />
                                </Identifier>
                              </ScalarOperator>
                            </RangeExpressions>
                          </Prefix>
                          <StartRange ScanType="GE">
                            <RangeColumns>
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_start" />
                            </RangeColumns>
                            <RangeExpressions>
                              <ScalarOperator ScalarString="(1390869967)">
                                <Const ConstValue="(1390869967)" />
                              </ScalarOperator>
                            </RangeExpressions>
                          </StartRange>
                          <EndRange ScanType="LE">
                            <RangeColumns>
                              <ColumnReference Database="[ThingDB]" Schema="[dbo]" Table="[Thing]" Alias="[t]" Column="time_start" />
                            </RangeColumns>
                            <RangeExpressions>
                              <ScalarOperator ScalarString="(1391869967)">
                                <Const ConstValue="(1391869967)" />
                              </ScalarOperator>
                            </RangeExpressions>
                          </EndRange>
                        </SeekKeys>
                      </SeekPredicateNew>
                    </SeekPredicates>
                  </IndexScan>
                </RelOp>
              </NestedLoops>
            </RelOp>
          </QueryPlan>
        </StmtSimple>
      </Statements>
    </Batch>
  </BatchSequence>
</ShowPlanXML>

Answer 1

来自IX_locations索引的Index Seek运算符的实际行数和估计行数之间存在大约十倍的差异。可能是统计数据陈旧，或者数据分布偏差。但这只是问题的一部分。

了解Thing table会更有趣。考虑到当你单独查询Things表时，在startTime列上进行过滤，它会在亚秒内返回，我的猜测是startTime更具选择性，而且这个查询在startTime列上使用了一些索引。

尝试从Things中选择一个#temp表并将其加入Locations。

此外，从Locations中选择#temp表并加入Thi​​ngs。检查执行计划，Things表上的运算符是什么？如果它再次寻求，那么我的建议是首先从事物和位置中选择#temp表，然后加入它们。