Function read_merged_rows 

pub(crate) fn read_merged_rows(
    group: &[FileSpan],
    from_ns: i64,
    to_ns: i64,
) -> MergedRows

Reads one slice of a file group, merged into time order without duplicates.

Each file whose span overlaps the slice is read with read_matching_rows, and the rows are combined with sort_and_drop_duplicates. A file that fails to read is logged and skipped, and the other files are still used.

Arguments

• group - Files from overlapping_file_groups, in file-name order.
• from_ns - Inclusive slice start, Unix nanoseconds.
• to_ns - Inclusive slice end, Unix nanoseconds.