Function discover_hive_partitioned_files 

pub fn discover_hive_partitioned_files(
    root: impl AsRef<Path>,
    file_pattern: Option<&str>,
) -> IngestionResult<Vec<PartitionedFile>>

Discover files under root whose parent path (relative to root) consists only of hive-style key=value directory segments.

• root must exist and be a directory.
• If file_pattern is Some, it is a glob::Pattern string matched against the path of each file relative to root (use forward slashes in the pattern for portability, e.g. **/*.csv).
• Results are sorted by Path for deterministic ordering.