private List<FieldRelation> buildFieldRelationByCustomFunction() {
        return Arrays
                .asList(new FieldRelation(new FieldInfo("id", new LongFormatInfo()),
                        new FieldInfo("id", new LongFormatInfo())),
                        new FieldRelation(new CustomFunction("`name`"),
                                new FieldInfo("name", new StringFormatInfo())),
                        new FieldRelation(new CustomFunction("ABS(age)"),
                                new FieldInfo("age", new IntFormatInfo())));
    }
Use content of field as a custom function
@return field relation
inlong-sort/sort-core/src/test/java/org/apache/inlong/sort/parser/CustomFunctionSqlParseTest.java