WP_Background_Process::is_queue_empty()

		protected function is_queue_empty() {
			global $wpdb;

			$table  = $wpdb->options;
			$column = 'option_name';

			if ( is_multisite() ) {
				$table  = $wpdb->sitemeta;
				$column = 'meta_key';
			}

			$key = $wpdb->esc_like( $this->identifier . '_batch_' ) . '%';

			$count = $wpdb->get_var( $wpdb->prepare( "
			SELECT COUNT(*)
			FROM {$table}
			WHERE {$column} LIKE %s
		", $key ) );

			return ( $count > 0 ) ? false : true;
		}