WP_Rewrite::page_uri_index

	public function page_uri_index() {
		global $wpdb;

		// Get pages in order of hierarchy, i.e. children after parents.
		$pages = $wpdb->get_results( "SELECT ID, post_name, post_parent FROM $wpdb->posts WHERE post_type = 'page' AND post_status != 'auto-draft'" );
		$posts = get_page_hierarchy( $pages );

		// If we have no pages get out quick.
		if ( ! $posts ) {
			return array( array(), array() );
		}

		// Now reverse it, because we need parents after children for rewrite rules to work properly.
		$posts = array_reverse( $posts, true );

		$page_uris            = array();
		$page_attachment_uris = array();

		foreach ( $posts as $id => $post ) {
			// URL => page name.
			$uri         = get_page_uri( $id );
			$attachments = $wpdb->get_results( $wpdb->prepare( "SELECT ID, post_name, post_parent FROM $wpdb->posts WHERE post_type = 'attachment' AND post_parent = %d", $id ) );
			if ( ! empty( $attachments ) ) {
				foreach ( $attachments as $attachment ) {
					$attach_uri                          = get_page_uri( $attachment->ID );
					$page_attachment_uris[ $attach_uri ] = $attachment->ID;
				}
			}

			$page_uris[ $uri ] = $id;
		}

		return array( $page_uris, $page_attachment_uris );
	}