Google Drive API: list files with no parent

Question

The files in Google domain that I administer have gotten into a bad state; there are thousands of files residing in the root directory. I want to identify these files and move them to a folder underneath "My Drive".

When I use the API to list the parents for one of these orphaned files, the result is an empty array. To determine if a file is orphaned, I can iterate over all the files in my domain, and request the list of parents for each. If the list is empty, I know that the file is orphaned.

But this is hideously slow.

Is there anyway to use the Drive API to search for files that have no parents?

The "parents" field for the q parameter doesn't seem to be useful for this, as it's only possible to specify that the parents list contains some ID.

Update:

I'm trying to find a quick way to locate items that are truly at the root of the document hierarchy. That is, they are siblings of "My Drive", not children of "My Drive".

Answer 1

In Java:

List<File> result = new ArrayList<File>();
Files.List request = drive.files().list();
request.setQ("'root'" + " in parents");

FileList files = null;
files = request.execute();

for (com.google.api.services.drive.model.File element : files.getItems()) {
    System.out.println(element.getTitle());
}

'root' is the parent folder, if the file or folder is in the root