func GetSystemVar(s *variable.SessionVars, key string) types.Datum {
	var d types.Datum
	key = strings.ToLower(key)
	sVal, ok := s.Systems[key]
	if ok {
		d.SetString(sVal)
	} else {
		// TiDBSkipConstraintCheck is a session scope vars. We do not store it in the global table.
		if key == variable.TiDBSkipConstraintCheck {
			d.SetString(variable.SysVars[variable.TiDBSkipConstraintCheck].Value)
		}
	}
	return d
}
// GetSystemVar gets a system variable.
GetSystemVar gets a system variable.
// GetSystemVar gets a system variable .
func GetSystemVar(s *variable.SessionVars, key string) types.Datum {
	var d types.Datum
	key = strings.ToLower(key)
	sVal, ok := s.Systems[key]
	if ok {
		d.SetString(sVal)
	} else {
		if key == variable.TiDBSkipConstraintCheck {
			d.SetString(variable.SysVars[variable.TiDBSkipConstraintCheck].Value)
		}
	}
	return d
}
func GetSystemVar ( s * variable . SessionVars , key string ) types . Datum { var d types . Datum key = strings . ToLower ( key ) sVal , ok := s . Systems [ key ] if ok { d . SetString ( sVal ) } else { if key == variable . TiDBSkipConstraintCheck { d . SetString ( variable . SysVars [ variable . TiDBSkipConstraintCheck ] . Value ) } } return d }
GetSystemVar gets a system variable.
GetSystemVar gets a system variable .
// TiDBSkipConstraintCheck is a session scope vars. We do not store it in the global table.