Application Insights Analytics执行子选择

Question

我在Application Insights中使用此引用documentation。

如何使用其他查询的输出进行子选择？

//Query 1
Events 
| where  Timestamp >= ago(30min) and Data contains('SomeString')
| project TraceToken

//I would like to use the first query's output in the subselect here.
Events 
| where TraceToken in ({I would like to use the First query's output here.})

在这种情况下，联接是否更好。哪个会有更好的表现。

Answer 1

您可以使用let语句来实现此目的。

以下是Analytics documentation的示例，我希望这会有所帮助：

let topCities =  toscalar ( // convert single column to value
   requests
   | summarize count() by client_City 
   | top 4 by count_ 
   | summarize makeset(client_City));
requests
| where client_City in (topCities) 
| summarize count() by client_City;

编辑：默认情况下，makeset()函数返回的最大元素数为128.应为较大的数据集指定MaxSetSize。