Azure DevOps Odata Group by child property is not working

Question

I am using the Azure DevOps Odata endpoints to retrieve data from my projects.

Now I face the problem that I am not able to group by the result based on a sub property of a workitem. The following ODATA query returns me an error message:

https://analytics.dev.azure.com/<organisation>/<project>/_odata/v2.0/WorkItems?
$filter=WorkItemType eq 'Activity'&
$select=AssignedTo/UserName,TotalCount&
$apply=groupby((AssignedTo/UserName, WorkItemType),aggregate($count as TotalCount))&
$expand=AssignedTo($select=UserName)

VS403483: The query specified in the URI is not valid: VS403522: The property 'AssignedTo' is not available on the specified Project(s). Please remove 'AssignedTo' from your query and try again..","innererror":{"message":"VS403522: The property 'AssignedTo' is not available on the specified Project(s). Please remove 'AssignedTo' from your query and try again.

{
    "State": "Closed",
    "AssignedTo": {
        "UserName": "User 2"
    }
},
{
    "State": "New",
    "AssignedTo": {
        "UserName": "User 1"
    }
}

When I try to do the same with a normal property, everything works fine:

https://analytics.dev.azure.com/<organisation>/<project>/_odata/v2.0/WorkItems?
$filter=WorkItemType eq 'Activity'&
$select=State,TotalCount&
$apply=groupby((State, WorkItemType),aggregate($count as TotalCount))

Answer 1

You can use the below query url.

https://analytics.dev.azure.com/{orgname}/{projectname}/_odata/v2.0/WorkItems?
$apply=filter(WorkItemType eq 'Bug')/groupby((AssignedTo/UserName, WorkItemType),aggregate($count as TotalCount))
&select=AssignedTo/UserName,TotalCount

And then you will get the result as below.

{
    "@odata.context": "https://analytics.dev.azure.com/{orgname}/{projectname}/_odata/v2.0/$metadata#WorkItems(AssignedTo(UserName),WorkItemType,TotalCount)",
    "value": [
        {
            "@odata.id": null,
            "WorkItemType": "Bug",
            "TotalCount": 3,
            "AssignedTo": {
                "@odata.id": null,
                "UserName": "{username1}"
            }
        },
        {
            "@odata.id": null,
            "WorkItemType": "Bug",
            "TotalCount": 4,
            "AssignedTo": {
                "@odata.id": null,
                "UserName": "{username2}"
            }
        }
    ]
}

Hope this help.