Querying local filesystem directory: How do I access the filename?

[Tim Harper]

With apache drill, I'm able to query a directory of JSON files just fine,
by invoking:

select * from file.`/path/to/data` t;

All of JSON files are selected, and the data comes as I'd expect. However,
no fields are returned describing from which file the data came. I'd like
to be able to use this signal in my query, in addition.

I apologize if this is clearly documented somewhere. I've looked and I'm
having a hard time.

This is the configuration for my file storage plugin:

{
  "type": "file",
  "enabled": true,
  "connection": "file:///",
  "workspaces": {
    "scimmia": {
      "location": "/home/scimmia",
      "writable": false,
      "defaultInputFormat": null
    }
  },
  "formats": {
    "json": {
      "type": "json"
    }
  }
}