WP_Posts_List_Table::_display_rows_hierarchical( array $pages, int $pagenum = 1, int $per_page = 20 )

850	private function _display_rows_hierarchical( $pages, $pagenum = 1, $per_page = 20 ) {851		global $wpdb;852 853		$level = 0;854 855		if ( ! $pages ) {856			$pages = get_pages( array( 'sort_column' => 'menu_order' ) );857 858			if ( ! $pages ) {859				return;860			}861		}862 863		/*864		 * Arrange pages into two parts: top level pages and children_pages.865		 * children_pages is two dimensional array. Example:866		 * children_pages[10][] contains all sub-pages whose parent is 10.867		 * It only takes O( N ) to arrange this and it takes O( 1 ) for subsequent lookup operations868		 * If searching, ignore hierarchy and treat everything as top level869		 */870		if ( empty( $_REQUEST['s'] ) ) {871			$top_level_pages = array();872			$children_pages  = array();873 874			foreach ( $pages as $page ) {875				// Catch and repair bad pages.876				if ( $page->post_parent === $page->ID ) {877					$page->post_parent = 0;878					$wpdb->update( $wpdb->posts, array( 'post_parent' => 0 ), array( 'ID' => $page->ID ) );879					clean_post_cache( $page );880				}881 882				if ( $page->post_parent > 0 ) {883					$children_pages[ $page->post_parent ][] = $page;884				} else {885					$top_level_pages[] = $page;886				}887			}888 889			$pages = &$top_level_pages;890		}891 892		$count      = 0;893		$start      = ( $pagenum - 1 ) * $per_page;894		$end        = $start + $per_page;895		$to_display = array();896 897		foreach ( $pages as $page ) {898			if ( $count >= $end ) {899				break;900			}901 902			if ( $count >= $start ) {903				$to_display[ $page->ID ] = $level;904			}905 906			++$count;907 908			if ( isset( $children_pages ) ) {909				$this->_page_rows( $children_pages, $count, $page->ID, $level + 1, $pagenum, $per_page, $to_display );910			}911		}912 913		// If it is the last pagenum and there are orphaned pages, display them with paging as well.914		if ( isset( $children_pages ) && $count < $end ) {915			foreach ( $children_pages as $orphans ) {916				foreach ( $orphans as $op ) {917					if ( $count >= $end ) {918						break;919					}920 921					if ( $count >= $start ) {922						$to_display[ $op->ID ] = 0;923					}924 925					++$count;926				}927			}928		}929