Function is_clean 

pub(crate) fn is_clean(
    parts: &[PartInfo],
    empty_files: usize,
    rows_repeated_within_files: usize,
) -> bool

Returns whether a folder is already clean: one file per window, no empty files, and no file holding the same row twice.

Files covering different single windows cannot share rows, so this proves there are no duplicates without merging anything.

Arguments

• parts - First-pass information for the non-empty part files.
• empty_files - Part files with no rows.
• rows_repeated_within_files - Rows that repeat another row of the same file.