presto-hive/src/main/java/io/prestosql/plugin/hive/GenericHiveRecordCursor.java/GenericHiveRecordCursor/getSlice
class GenericHiveRecordCursor:    @Override
    public Slice getSlice(int fieldId)
    {
        checkState(!closed, "Cursor is closed");

        validateType(fieldId, Slice.class);
        if (!loaded[fieldId]) {
            parseStringColumn(fieldId);
        }
        return slices[fieldId];
    }