presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/systemtables/ShardMetadataRecordCursor.java/ShardMetadataRecordCursor/isNull
class ShardMetadataRecordCursor:    @Override
    public boolean isNull(int field)
    {
        checkState(!closed, "cursor is closed");
        checkPositionIndex(field, TYPES.size());
        return resultSetValues.isNull(field);
    }