( $i = 0; $i < $chunks; $i++ ) {
			$indexNumber = 1 < $chunks ? $i + 1 : '';

			$usersTableName = aioseo()->core->db->db->users; // We get the table name from WPDB since multisites share the same table.
			$lastModified   = aioseo()->core->db->start( "$usersTableName as u", true )
				->select( 'MAX(p.post_modified_gmt) as lastModified' )
				->join( 'posts as p', 'u.ID = p.post_author' )
				->where( 'p.post_status', 'publish' )
				->whereIn( 'p.post_type', $postTypes )
				->groupBy( 'u.ID' )
				->orderBy( 'lastModified DESC' )
				->limit( aioseo()->sitemap->linksPerIndex, $i * aioseo()->sitemap->linksPerIndex )
				->run()
				->result();

			$lastModified = ! empty( $lastModified[0]->lastModified ) ? aioseo()->helpers->dateTimeToIso8601( $lastModified[0]->lastModified ) : '';

			$index = [
				'loc'     => aioseo()->helpers->localizedUrl( "/author-$filename$indexNumber.xml" ),
				'lastmod' => $lastModified,
				'count'   => $i + 1 === $chunks ? $amountOfAuthors % aioseo()->sitemap->linksPerIndex : aioseo()->sitemap->linksPerIndex
			];

			$indexes[] = $index;
		}

		return $indexes;
	}

	/**
	 * Builds indexes for all eligible posts of a given post type.
	 *
	 * @since 4.0.0
	 *
	 * @param  string $postType The post type.
	 * @return array            The indexes.
	 */
	private function buildIndexesPostType( $postType ) {
		$prefix                 = aioseo()->core->db->prefix;
		$postsTable             = $prefix . 'posts';
		$aioseoPostsTable       = $prefix . 'aioseo_posts';
		$termRelationshipsTable = $prefix . 'term_relationships';
		$termTaxonomyTable      = $prefix . 'term_taxonomy';
		$termsTable             = $prefix . 'terms';
		$linksPerIndex          = aioseo()->sitemap->linksPerIndex;

		if ( 'attachment' === $postType && 'disabled' !== aioseo()->dynamicOptions->searchAppearance->postTypes->attachment->redirectAttachmentUrls ) {
			return [];
		}

		$excludedPostIds = [];
		$excludedTermIds = aioseo()->sitemap->helpers->excludedTerms();
		if ( ! empty( $excludedTermIds ) ) {
			$excludedTermIds = explode( ', ', $excludedTermIds );
			$excludedPostIds = aioseo()->core->db->start( 'term_relationships' )
				->select( 'object_id' )
				->whereIn( 'term_taxonomy_id', $excludedTermIds )
				->run()
				->result();

			$excludedPostIds = array_map( function( $post ) {
				return $post->object_id;
			}, $excludedPostIds );
		}

		$whereClause         = '';
		$excludedPostsString = aioseo()->sitemap->helpers->excludedPosts();
		if ( ! empty( $excludedPostsString ) ) {
			$excludedPostIds = array_merge( $excludedPostIds, explode( ', ', $excludedPostsString ) );
		}

		if ( ! empty( $excludedPostIds ) ) {
			$implodedPostIds = aioseo()->helpers->implodeWhereIn( $excludedPostIds, true );
			$whereClause     = "AND p.ID NOT IN ( $implodedPostIds )";
		}

		if (
			apply_filters( 'aioseo_sitemap_woocommerce_exclude_hidden_products', true ) &&
			aioseo()->helpers->isWooCommerceActive() &&
			'product' === $postType
		) {
			$whereClause .= " AND p.ID NOT IN (
				SELECT CONVERT(tr.object_id, unsigned) AS object_id
				FROM {$termRelationshipsTable} AS tr
				JOIN {$termTaxonomyTable} AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
				JOIN {$termsTable} AS t ON tt.term_id = t.term_id
				WHERE t.name = 'exclude-from-catalog'
			)";
		}

		$posts = aioseo()->core->db->execute(
			aioseo()->core->db->db->prepare(
				"SELECT ID, post_modified_gmt
				FROM (
					SELECT @row := @row + 1 AS rownum, ID, post_modified_gmt
					FROM (
						SELECT p.ID, ap.priority, p.post_modified_gmt
						FROM {$postsTable} AS p
						LEFT JOIN {$aioseoPostsTable} AS ap ON p.ID = ap.post_id
						WHERE p.post_status IN ( 'publish', 'inherit' )
							AND p.post_type = %s
							AND p.post_password = ''
							AND (ap.robots_noindex IS NULL OR ap.robots_default = 1 OR ap.robots_noindex = 0)
							{$whereClause}
						ORDER BY ap.priority DESC, p.post_modified_gmt DESC
					) AS x
					CROSS JOIN (SELECT @row := 0) AS vars
					ORDER BY post_modified_gmt DESC
				) AS y
				WHERE rownum = 1 OR rownum % %d = 1;",
				[
					$postType,
					$linksPerIndex
				]
			),
			true
		)->result();

		$totalPosts = aioseo()->core->db->execute(
			aioseo()->core->db->db->prepare(
				"SELECT COUNT(*) as count
				FROM {$postsTable} as p
				LEFT JOIN {$aioseoPostsTable} as ap ON p.ID = ap.post_id
				WHERE p.post_status IN ( 'publish', 'inherit' )
					AND p.post_type = %s
					AND p.post_password = ''
					AND (ap.robots_noindex IS NULL OR ap.robots_default = 1 OR ap.robots_noindex = 0)
					{$whereClause}
				",
				[
					$postType
				]
			),
			true
		)->result();

		if ( $posts ) {
			$indexes   = [];
			$filename  = aioseo()->sitemap->filename;
			$postCount = count( $posts );
			for ( $i = 0; $i < $postCount; $i++ ) {
				$indexNumber = 0 !== $i && 1 < $postCount ? $i + 1 : '';

				$indexes[] = [
					'loc'     => aioseo()->helpers->localizedUrl( "/$postType-$filename$indexNumber.xml" ),
					'lastmod' => aioseo()->helpers->dateTimeToIso8601( $posts[ $i ]->post_modified_gmt ),
					'count'   => $linksPerIndex
				];
			}

			// We need to update the count of the last index since it won't necessarily be the same as the links per index.
			$indexes[ count( $indexes ) - 1 ]['count'] = $totalPosts[0]->count - ( $linksPerIndex * ( $postCount - 1 ) );

			return $indexes;
		}

		if ( ! $posts ) {
			$addonsPosts = aioseo()->addons->doAddonFunction( 'root', 'buildIndexesPostType', [ $postType ] );

			foreach ( $addonsPosts as $addonPosts ) {
				if ( $addonPosts ) {
					$posts = $addonPosts;
					break;
				}
			}
		}

		if ( ! $posts ) {
			return [];
		}

		return $this->buildIndexes( $postType, $posts );
	}

	/**
	 * Builds indexes for all eligible terms of a given taxonomy.
	 *
	 * @since 4.0.0
	 *
	 * @param  string $taxonomy The taxonomy.
	 * @return array            The indexes.
	 */
	private function buildIndexesTaxonomy( $taxonomy ) {
		$terms = aioseo()->sitemap->content->terms( $taxonomy, [ 'root' => true ] );

		if ( ! $terms ) {
			$addonsTerms = aioseo()->addons->doAddonFunction( 'root', 'buildIndexesTaxonomy', [ $taxonomy ] );

			foreach ( $addonsTerms as $addonTerms ) {
				if ( $addonTerms ) {
					$terms = $addonTerms;
					break;
				}
			}
		}

		if ( ! $terms ) {
			return [];
		}

		return $this->buildIndexes( $taxonomy, $terms );
	}

	/**
	 * Builds indexes for a given type.
	 *
	 * Acts as a helper function for buildIndexesPostTypes() and buildIndexesTaxonomies().
	 *
	 * @since 4.0.0
	 *
	 * @param  string $name    The name of the object parent.
	 * @param  array  $entries The sitemap entries.
	 * @return array           The indexes.
	 */
	public function buildIndexes( $name, $entries ) {
		$filename = aioseo()->sitemap->filename;
		$chunks   = aioseo()->sitemap->helpers->chunkEntries( $entries );
		$indexes  = [];
		for ( $i = 0; $i < count( $chunks ); $i++ ) {
			$chunk       = array_values( $chunks[ $i ] );
			$indexNumber = 0 !== $i && 1 < count( $chunks ) ? $i + 1 : '';

			$index = [
				'loc'   => aioseo()->helpers->localizedUrl( "/$name-$filename$indexNumber.xml" ),
				'count' => count( $chunks[ $i ] )
			];

			if ( isset( $entries[0]->ID ) ) {
				$ids = array_map( function( $post ) {
					return $post->ID;
				}, $chunk );
				$ids = implode( "', '", $ids );

				$lastModified = null;
				if ( ! apply_filters( 'aioseo_sitemap_lastmod_disable', false ) ) {
					$lastModified = aioseo()->core->db
						->start( aioseo()->core->db->db->posts . ' as p', true )
						->select( 'MAX(`p`.`post_modified_gmt`) as last_modified' )
						->whereRaw( "( `p`.`ID` IN ( '$ids' ) )" )
						->run()
						->result();
				}

				if ( ! empty( $lastModified[0]->last_modified ) ) {
					$index['lastmod'] = aioseo()->helpers->dateTimeToIso8601( $lastModified[0]->last_modified );
				}
				$indexes[] = $index;
				continue;
			}

			$termIds = [];
			foreach ( $chunk as $term ) {
				$termIds[] = $term->term_id;
			}
			$termIds = implode( "', '", $termIds );

			$termRelationshipsTable = aioseo()->core->db->db->prefix . 'term_relationships';

			$lastModified = null;
			if ( ! apply_filters( 'aioseo_sitemap_lastmod_disable', false ) ) {
				$lastModified = aioseo()->core->db
					->start( aioseo()->core->db->db->posts . ' as p', true )
					->select( 'MAX(`p`.`post_modified_gmt`) as last_modified' )
					->whereRaw( "
					( `p`.`ID` IN
						(
							SELECT CONVERT(`tr`.`object_id`, unsigned)
							FROM `$termRelationshipsTable` as tr
							WHERE `tr`.`term_taxonomy_id` IN ( '$termIds' )
						)
					)" )
					->run()
					->result();
			}

			if ( ! empty( $lastModified[0]->last_modified ) ) {
				$index['lastmod'] = aioseo()->helpers->dateTimeToIso8601( $lastModified[0]->last_modified );
			}
			$indexes[] = $index;
		}

		return $indexes;
	}
}