errNonTimestampArg   = errors.New("Expected a timestamp argument")
)

func (e *FuncExpr) getFunctionName() FuncName {
	switch {
	case e.SFunc != nil:
		return FuncName(strings.ToUpper(e.SFunc.FunctionName))
	case e.Count != nil:
		return aggFnCount
	case e.Cast != nil:
		return sqlFnCast
	case e.Substring != nil:
		return sqlFnSubstring
	case e.Extract != nil:
		return sqlFnExtract