@Override
    public void process(boolean validate, boolean documentsOnly) {
        SDDocumentType document = schema.getDocument();
        if (document != null) {
            for (SDField field : schema.extraFieldList()) {
                addSdField(schema, document, field, validate);
            }
            for (var docsum : schema.getSummaries().values()) {
                for (var summaryField : docsum.getSummaryFields().values()) {
                    considerCopyTransformForExtraSummaryField(schema, summaryField);
                }
            }
        }
    }
This processor creates a {@link com.yahoo.schema.document.SDDocumentType} for each {@link Schema}
object which holds all the data that search
associates with a document described in a search definition file. This includes all extra fields, summary fields and
implicit fields. All non-indexed and non-summary fields are discarded.
config-model/src/main/java/com/yahoo/schema/processing/AddExtraFieldsToDocument.java