Why does my ADX cluster policy request classification fail?

Question

I created a custom Workload Group called "ConcurrentWorkloadGroup". I then attempt to create a policy request classification with the following KQL command:

.alter cluster policy request_classification '{"IsEnabled":true}' <|
    iff(
        request_properties.request_type == "Query"
        and request_properties.current_database == "<db_name>"
        and request_properties.request_description  == "concurrent",
        "ConcurrentWorkloadGroup",
        "default"
    )

I attempt to query using the new Workload Group:

set request_description = "concurrent";
<db_name>
| take 10

When I run .show queries to check the Workload Group, it shows the query uses the default group. When I remove the request_description line, the query uses the new Workload Group.

Ultimately, I want to be able to choose which Workload Group is being used from a subset of my queries, so I welcome other ways to achieve this so long is it doesn't affect the group of other queries.

Answer 1

Reading this (https://learn.microsoft.com/en-us/azure/data-explorer/kusto/api/rest/request-properties), I thought I would be able to set the property using the KQL set statement.

I've now found a note in another separate doc saying this cannot be done with the set statement.