Null for a folder, and for a file written without one.
The parent folder's path, segments joined with /; "" is the root.
The document's public id: bdoc_…, cdoc_….
The object's S3 key; null for a folder.
The file's or folder's own path segment.
In bytes; null for a folder.
The dashboard user's public id; null when the last writer was not one.
One row of a document index: a file, or a folder that holds them.