wp_upgrade()

645	function wp_upgrade() {646		global $wp_current_db_version, $wp_db_version;647 648		$wp_current_db_version = (int) __get_option( 'db_version' );649 650		// We are up to date. Nothing to do.651		if ( $wp_db_version === $wp_current_db_version ) {652			return;653		}654 655		if ( ! is_blog_installed() ) {656			return;657		}658 659		wp_check_mysql_version();660		wp_cache_flush();661		pre_schema_upgrade();662		make_db_current_silent();663		upgrade_all();664		if ( is_multisite() && is_main_site() ) {665			upgrade_network();666		}667		wp_cache_flush();668 669		if ( is_multisite() ) {670			update_site_meta( get_current_blog_id(), 'db_version', $wp_db_version );671			update_site_meta( get_current_blog_id(), 'db_last_updated', microtime() );672		}673 674		delete_transient( 'wp_core_block_css_files' );675 676		/**677		 * Fires after a site is fully upgraded.678		 *679		 * @since 3.9.0680		 *681		 * @param int $wp_db_version         The new $wp_db_version.682		 * @param int $wp_current_db_version The old (current) $wp_db_version.683		 */684		do_action( 'wp_upgrade', $wp_db_version, $wp_current_db_version );685	}