private void generateSyntheticStatementsForUntouchedFields(Builder ilscriptBuilder, Set<String> touchedFields) {
        Set<String> fieldsWithSyntheticStatements = new HashSet<>(docFields);
        fieldsWithSyntheticStatements.removeAll(touchedFields);
        List<String> orderedFields = new ArrayList<>(fieldsWithSyntheticStatements);
        Collections.sort(orderedFields);
        for (String fieldName : orderedFields) {
            StatementExpression copyField = new StatementExpression(new InputExpression(fieldName),
                    new PassthroughExpression(fieldName));
            ilscriptBuilder.content(copyField.toString());
        }
    }
An indexing language script derived from a schema. An indexing script contains a set of indexing
statements, organized in a composite structure of indexing code snippets.

@author bratseth
config-model/src/main/java/com/yahoo/schema/derived/IndexingScript.java