Function load_partition_metadata 

pub fn load_partition_metadata(
    object_store: &Arc<dyn ObjectStore>,
    path: &Path,
    file_size: u64,
    cache: Option<&MetadataCache>,
) -> impl Future<Output = Result<Arc<ParquetMetaData>, ParquetError>>

Read and parse a partition’s parquet footer directly from object_store — the sole partition-metadata read path. Checks and backfills the shared MetadataCache parsed-lookaside: on a cache hit this returns immediately, on a miss it reads the footer from object_store (which may itself be L1-cache-backed) and stores the parsed result before returning it.