public function get_session( $customer_id, $default = false ) {
		global $wpdb;

		if ( Constants::is_defined( 'WP_SETUP_CONFIG' ) ) {
			return false;
		}

		// Try to get it from the cache, it will return false if not present or if object cache not in use.
		$value = wp_cache_get( $this->get_cache_prefix() . $customer_id, WC_SESSION_CACHE_GROUP );

		if ( false === $value ) {
			$value = $wpdb->get_var( $wpdb->prepare( "SELECT session_value FROM $this->_table WHERE session_key = %s", $customer_id ) ); // @codingStandardsIgnoreLine.

			if ( is_null( $value ) ) {
				$value = $default;
			}

			$cache_duration = $this->_session_expiration - time();
			if ( 0 < $cache_duration ) {
				wp_cache_add( $this->get_cache_prefix() . $customer_id, $value, WC_SESSION_CACHE_GROUP, $cache_duration );
			}
		}

		return maybe_unserialize( $value );
	}