presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/systemtables/ShardMetadataRecordCursor.java/ShardMetadataRecordCursor/advanceNextPosition
class ShardMetadataRecordCursor:    @Override
    public boolean advanceNextPosition()
    {
        if (resultSet == null) {
            close();
        }

        if (closed) {
            return false;
        }

        try {
            while (!resultSet.next()) {
                resultSet = getNextResultSet();
                if (resultSet == null) {
                    close();
                    return false;
                }
            }
            completedBytes += resultSetValues.extractValues(
                    resultSet,
                    ImmutableSet.of(getColumnIndex(SHARD_METADATA, SHARD_UUID)),
                    ImmutableSet.of(getColumnIndex(SHARD_METADATA, XXHASH64)));
            return true;
        }
        catch (SQLException | DBIException e) {
            throw metadataError(e);
        }
    }