How can I create a recursive query using KQL? - azure-application-insights

Question

everyone!
Do you know how can I create a recursive query using KQL in application insights?
Just to give you a context: As you know, currently there is a hierarchical relationship between the tables requests and dependencies in application insights by the id and operation_ParentId columns:
->(system A) request id=req_1, parent_id=dep_1
-> (system B) dependency id=dep_2, parent_id=req_1
->(system C) request id=req_3, parent_id=dep_2
I'm trying to build a tree view in my Workbook to have a better distributed tracing visualization and consequently know what happened in a specific request.
Do you know if there's something I can use to archive that goal?

Answer 1

Here is a quick example for how you can work with hierarchical data using multiple JOINs.
Please note that you must assume the depth of the tree and matched the number of JOINs to that assumption, e.g., in the following example I assumed there are no more than 7 hierarchy levels.
In the following example we traverse from the root to the leaves.
In the result data set, we get a record of every leaf in the hierarchical tree.
let t = datatable(id:int, pid:int)
[
1 ,-1
,2 ,1
,3 ,1
,4 ,2
,5 ,2
,6 ,2
,7 ,3
,8 ,7
,9 ,8
,10 ,8
];
t
| where pid == -1
| join kind=leftouter t on $left.id == $right.pid
| join kind=leftouter t on $left.id1 == $right.pid
| join kind=leftouter t on $left.id2 == $right.pid
| join kind=leftouter t on $left.id3 == $right.pid
| join kind=leftouter t on $left.id4 == $right.pid
| join kind=leftouter t on $left.id5 == $right.pid
| join kind=leftouter t on $left.id6 == $right.pid
| project-away pid*
id
id1
id2
id3
id4
id5
id6
id7
1
3
7
8
9
1
3
7
8
10
1
2
6
1
2
5
1
2
4
Fiddle
In the following example we traverse from each node (of any kind), up to the root.
let t = datatable(id:int, pid:int)
[
1 ,-1
,2 ,1
,3 ,1
,4 ,2
,5 ,2
,6 ,2
,7 ,3
,8 ,7
,9 ,8
,10 ,8
];
t
| join kind=leftouter t on $left.pid == $right.id
| join kind=leftouter t on $left.pid1 == $right.id
| join kind=leftouter t on $left.pid2 == $right.id
| join kind=leftouter t on $left.pid3 == $right.id
| join kind=leftouter t on $left.pid4 == $right.id
| join kind=leftouter t on $left.pid5 == $right.id
| join kind=leftouter t on $left.pid6 == $right.id
| project-away pid*
id
id1
id2
id3
id4
id5
id6
id7
10
8
7
3
1
9
8
7
3
1
6
2
1
5
2
1
4
2
1
7
3
1
1
3
1
2
1
8
7
3
1
Fiddle