在KQL用户功能中使用column_ifexists

问题描述

我正在尝试从具有动态内容的枢轴内容创建函数。我的情况的一个示例如下所示：

let countActivities = (col: string) {
    array_length(column_ifexists(col,dynamic([])))
};
let testdata = datatable(ActivityId: string,Message: string,SessionId: string)
    ["1","abc","100","2","def","ghi","4","jkl","1","mno","200"];
testdata
| extend iActivityId = toint(ActivityId)
| evaluate pivot(iActivityId,make_set(Message),SessionId)
| project SessionId,Has1 = countActivities("1"),Has2 = countActivities("2"),Has3 = countActivities("3"),Has4 = countActivities("4");

我希望上面的countActivities返回动态列的数组中的元素数，但是上面的结果会导致错误columnifexists(): cannot be used in the function without tabular argument。我希望这是一个标量函数，所以不确定在这种情况下如何提供表格参数。

上面的countActivities应该如何编写以允许这样做？

解决方法

一列只能存在于表格表达式（例如表格）中。 您的原始函数没有这样的内容（即您希望这些列在哪里存在？），因此会看到错误消息。

以下替代方案如何？

let f = (arr:dynamic,col: string) {
    array_index_of(arr,col) != -1
};
let testdata = datatable(ActivityId: string,Message: string,SessionId: string)
    ["1","abc","100","2","def","ghi","4","jkl","1","mno","200"];
testdata
| summarize make_set(ActivityId) by SessionId
| project SessionId,Has1 = f(set_ActivityId,"1"),Has2 = f(set_ActivityId,"2"),Has3 = f(set_ActivityId,"3"),Has4 = f(set_ActivityId,"4")

->

SessionId   Has1    Has2    Has3    Has4
100         TRUE    TRUE    FALSE   TRUE
200         TRUE    FALSE   FALSE   FALSE