presto-main/src/main/java/io/prestosql/sql/gen/ExpressionCompiler.java/ExpressionCompiler/compile
class ExpressionCompiler:    private <T> Class<? extends T> compile(Optional<RowExpression> filter, List<RowExpression> projections, BodyCompiler bodyCompiler, Class<? extends T> superType)
    {
        // create filter and project page iterator class
        try {
            return compileProcessor(filter.orElse(constant(true, BOOLEAN)), projections, bodyCompiler, superType);
        }
        catch (CompilationException e) {
            throw new PrestoException(COMPILER_ERROR, e.getCause());
        }
    }