private boolean fieldIsExtraSummaryField(Schema schema, String name) {
        var field = schema.getConcreteField(name);
        return field == null;
    }
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