Function fetch_root_headline_related_paragraph 

pub async fn fetch_root_headline_related_paragraph(
    conn: &mut SqliteConnection,
    headline_per_page: u8,
    headline_page: u32,
) -> Result<IndexMap<i64, IndexMap<i64, Item>>, Error>

親が存在しない見出しとそれらに紐づいた段落を取得します。

SELECT *
FROM view_deserializable_item
WHERE item_type = 'paragraph'
  AND p_headline_id IN (SELECT id
                        FROM headlines
                        WHERE parent_id IS NULL
                        ORDER BY headline_pos NULLS LAST
                        LIMIT ? OFFSET ?)
ORDER BY p_paragraph_pos NULLS LAST;