presto-main/src/main/java/io/prestosql/execution/ParameterExtractor.java/ParameterExtractor/getParameterCount
class ParameterExtractor:    public static int getParameterCount(Statement statement)
    {
        ParameterExtractingVisitor parameterExtractingVisitor = new ParameterExtractingVisitor();
        parameterExtractingVisitor.process(statement, null);
        return parameterExtractingVisitor.getParameters().size();
    }