presto-main/src/main/java/io/prestosql/sql/analyzer/ExpressionTreeUtils.java/ExpressionTreeUtils/asQualifiedName
class ExpressionTreeUtils:    public static QualifiedName asQualifiedName(Expression expression)
    {
        QualifiedName name = null;
        if (expression instanceof Identifier) {
            name = QualifiedName.of(((Identifier) expression).getValue());
        }
        else if (expression instanceof DereferenceExpression) {
            name = DereferenceExpression.getQualifiedName((DereferenceExpression) expression);
        }
        return name;
    }