private void addField(Schema schema, SDDocumentType document, Field field, boolean validate) {
        if (document.getField(field.getName()) != null && !(document.getField(field.getName()) == field)) {
            if (validate)
                throw newProcessException(schema, field, "Field shadows another.");
        }
        document.addField(field);
    }
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