帮助解释执行计划（哈希聚合）
Geo*_*ios 6 sql-server optimization execution-plan
所以我有一个我正在尝试优化的执行计划，并且有一段我不太明白的操作符。
计划中有一部分使用了计算标量，然后是使用哈希匹配的聚合。
我有一个问题：
如何使用哈希匹配聚合器的属性来告诉我它输出的是哪些列？我不知道正在对哪些列执行聚合。
这是计划的部分：
这是运算符属性：
为元素规划 XML：
<RelOp NodeId="489" PhysicalOp="Hash Match" LogicalOp="Aggregate" EstimateRows="25432.8" EstimateIO="0" EstimateCPU="621.202" AvgRowSize="1038" EstimatedTotalSubtreeCost="12113" Parallel="0" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row">
<OutputList>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="id" />
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="description" />
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="unitPrice" />
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="units" />
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="billCurrencyAmount" />
<ColumnReference Table="#BillLineCategorisation" Alias="[blc]" Column="Item" />
<ColumnReference Table="#BillLineCategorisation" Alias="[blc]" Column="InvoiceLineCategory" />
<ColumnReference Column="Expr1066" />
<ColumnReference Column="Expr1067" />
<ColumnReference Column="Expr1068" />
<ColumnReference Column="Expr1069" />
<ColumnReference Column="Expr1070" />
<ColumnReference Column="Expr1071" />
<ColumnReference Column="Expr1072" />
<ColumnReference Column="Expr1073" />
<ColumnReference Column="Expr1074" />
<ColumnReference Column="Expr1075" />
<ColumnReference Column="Expr1076" />
<ColumnReference Column="Expr1077" />
<ColumnReference Column="Expr1078" />
<ColumnReference Column="Expr1079" />
</OutputList>
<MemoryFractions Input="0.00395919" Output="0.379612" />
<Hash>
<DefinedValues>
<DefinedValue>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="description" />
<ScalarOperator ScalarString="ANY([Staging].[Junifer].[BillBreakdownLine].[description] as [bbl].[description])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="description" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
<DefinedValue>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="unitPrice" />
<ScalarOperator ScalarString="ANY([Staging].[Junifer].[BillBreakdownLine].[unitPrice] as [bbl].[unitPrice])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="unitPrice" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
<DefinedValue>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="units" />
<ScalarOperator ScalarString="ANY([Staging].[Junifer].[BillBreakdownLine].[units] as [bbl].[units])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="units" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
<DefinedValue>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="billCurrencyAmount" />
<ScalarOperator ScalarString="ANY([Staging].[Junifer].[BillBreakdownLine].[billCurrencyAmount] as [bbl].[billCurrencyAmount])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="billCurrencyAmount" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
<DefinedValue>
<ColumnReference Column="Expr1077" />
<ScalarOperator ScalarString="ANY([Expr1077])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1077" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
<DefinedValue>
<ColumnReference Column="Expr1078" />
<ScalarOperator ScalarString="ANY([Expr1078])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1078" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
<DefinedValue>
<ColumnReference Column="Expr1079" />
<ScalarOperator ScalarString="ANY([Expr1079])">
<Aggregate Distinct="0" AggType="ANY">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1079" />
</Identifier>
</ScalarOperator>
</Aggregate>
</ScalarOperator>
</DefinedValue>
</DefinedValues>
<HashKeysBuild>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="id" />
<ColumnReference Column="Expr1066" />
<ColumnReference Column="Expr1067" />
<ColumnReference Column="Expr1068" />
<ColumnReference Column="Expr1069" />
<ColumnReference Column="Expr1070" />
<ColumnReference Column="Expr1071" />
<ColumnReference Column="Expr1072" />
<ColumnReference Table="#BillLineCategorisation" Alias="[blc]" Column="Item" />
<ColumnReference Table="#BillLineCategorisation" Alias="[blc]" Column="InvoiceLineCategory" />
<ColumnReference Column="Expr1073" />
<ColumnReference Column="Expr1074" />
<ColumnReference Column="Expr1075" />
<ColumnReference Column="Expr1076" />
</HashKeysBuild>
<BuildResidual>
<ScalarOperator ScalarString="[Staging].[Junifer].[BillBreakdownLine].[id] as [bbl].[id] = [Staging].[Junifer].[BillBreakdownLine].[id] as [bbl].[id] AND [Expr1066] = [Expr1066] AND [Expr1067] = [Expr1067] AND [Expr1068] = [Expr1068] AND [Expr1069] = [Expr1069] AND [Expr1070] = [Expr1070] AND [Expr1071] = [Expr1071] AND [Expr1072] = [Expr1072] AND #BillLineCategorisation.[Item] as [blc].[Item] = #BillLineCategorisation.[Item] as [blc].[Item] AND #BillLineCategorisation.[InvoiceLineCategory] as [blc].[InvoiceLineCategory] = #BillLineCategorisation.[InvoiceLineCategory] as [blc].[InvoiceLineCategory] AND [Expr1073] = [Expr1073] AND [Expr1074] = [Expr1074] AND [Expr1075] = [Expr1075] AND [Expr1076] = [Expr1076]">
<Logical Operation="AND">
... <Logical Operation="AND">
<ScalarOperator>
<Compare CompareOp="IS">
<ScalarOperator>
<Identifier>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="id" />
</Identifier>
</ScalarOperator>
<ScalarOperator>
<Identifier>
<ColumnReference Database="[Staging]" Schema="[Junifer]" Table="[BillBreakdownLine]" Alias="[bbl]" Column="id" />
</Identifier>
</ScalarOperator>
</Compare>
</ScalarOperator>
<ScalarOperator>
<Compare CompareOp="IS">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1066" />
</Identifier>
</ScalarOperator>
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1066" />
</Identifier>
</ScalarOperator>
</Compare>
</ScalarOperator>
</Logical>
</ScalarOperator>
<ScalarOperator>
<Compare CompareOp="IS">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1067" />
</Identifier>
</ScalarOperator>
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1067" />
</Identifier>
</ScalarOperator>
</Compare>
</ScalarOperator>
</Logical>
</ScalarOperator>
<ScalarOperator>
<Compare CompareOp="IS">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1068" />
</Identifier>
</ScalarOperator>
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1068" />
</Identifier>
</ScalarOperator>
</Compare>
</ScalarOperator>
</Logical>
</ScalarOperator>
<ScalarOperator>
<Compare CompareOp="IS">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1069" />
</Identifier>
</ScalarOperator>
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1069" />
</Identifier>
</ScalarOperator>
</Compare>
</ScalarOperator>
</Logical>
</ScalarOperator>
<ScalarOperator>
<Compare CompareOp="IS">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1070" />
</Identifier>
</ScalarOperator>
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1070" />
</Identifier>
</ScalarOperator>
</Compare>
</ScalarOperator>
</Logical>
</ScalarOperator>
<ScalarOperator>
如何使用哈希匹配聚合器的属性来告诉我它正在输出哪些列？
它清楚地显示在 XML 的输出列表中。当您看到表达式时，您需要回溯并找出表达式定义是什么。
由于我看不到您的完整查询和执行计划，我将使用一个示例来展示如何获取该信息。
SELECT DISTINCT [PickedQuantity]
FROM [WideWorldImporters].[Sales].[OrderLines]
在这种情况下是这样的PickedQuantity。
现在，如果我将相同的查询扩展到您，您将看到您在案例中看到的列比较。
SELECT DISTINCT
[PickedQuantity],
[LastEditedBy],
[LastEditedWhen]
FROM
[WideWorldImporters].[Sales].[OrderLines]
您可以在 XML 中看到相同的内容。
我无法判断正在对哪些列执行聚合。
正如您所说，您的 select 语句中有不同的内容，我假设这就是您看到Hash Aggregate运算符的原因。您可以在上面的示例中看到使用Hash Aggregate来实现DISTINCT.
Paul White 的这篇文章通过复杂的示例提供了更多见解。
Craig Freedman 的这篇文章展示了用于实现的哈希聚合的示例DISTINCT。