errNonStringTrimArg  = errors.New("TRIM() received a non-string argument")
	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:

	case e.FuncCall != nil:
		return e.FuncCall.evalNode(r, tableAlias)
	}
	return nil, errInvalidASTNode
}

func (e *FuncExpr) evalNode(r Record, tableAlias string) (res *Value, err error) {
	switch e.getFunctionName() {
	case aggFnCount, aggFnAvg, aggFnMax, aggFnMin, aggFnSum:
		return e.getAggregate()
	default:
		return e.evalSQLFnNode(r, tableAlias)
	}
}