return e.JPathExpr.evalNode(r, tableAlias)
	case e.ListExpr != nil:
		return e.ListExpr.evalNode(r, tableAlias)
	case e.SubExpression != nil:
		return e.SubExpression.evalNode(r, tableAlias)
	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() {

	JPathExpr     *JSONPath   `parser:"| @@"`
	ListExpr      *ListExpr   `parser:"| @@"`
	SubExpression *Expression `parser:"| \"(\" @@ \")\""`
	// Include function expressions here.
	FuncCall *FuncExpr `parser:"| @@"`
}

// FuncExpr represents a function call
type FuncExpr struct {
	SFunc     *SimpleArgFunc `parser:"  @@"`
	Count     *CountFunc     `parser:"| @@"`