Metric field

Hi,

I was investigating on TopNMetricSpec and i saw that it’s used like that:

"metric": {
    "type": "numeric",
    "metric": "<metric_name>"
}

I just want to know where use this metric field. (Query, Ingestion, …) ?

Thanks,

Ben

For the ones who wants to know:

http://druid.io/docs/latest/querying/topnquery.html