```
milovidov-desktop :) CREATE TABLE perf_lc_num(　        num UInt8,　        arr Array(LowCardinality(Int64)) default [num]　        ) ENGINE = TinyLog

CREATE TABLE perf_lc_num
(
    `num` UInt8,
    `arr` Array(LowCardinality(Int64)) DEFAULT [num]
)
ENGINE = TinyLog

Query id: e95f9a71-5795-4dea-8d80-4729fc8016b9

Ok.

0 rows in set. Elapsed: 0.002 sec. 

milovidov-desktop :) INSERT INTO perf_lc_num (num)
:-]         SELECT toUInt8(number)
:-]         FROM numbers(100000000)

INSERT INTO perf_lc_num (num) SELECT toUInt8(number)
FROM numbers(100000000)

Query id: 1101fd75-a545-4809-acb5-8afa2fae80c0


Received exception from server (version 20.13.1):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: Got empty stream for DataTypeLowCardinality keys.: While executing SinkToOutputStream. 

0 rows in set. Elapsed: 0.045 sec. 

milovidov-desktop :) INSERT INTO perf_lc_num (num)　        SELECT toUInt8(number)　        FROM numbers(100000000)

INSERT INTO perf_lc_num (num) SELECT toUInt8(number)
FROM numbers(100000000)

Query id: 0ad8532a-5c6e-4590-84cd-7e00759d152d


Received exception from server (version 20.13.1):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: Got empty stream for DataTypeLowCardinality keys.: While executing SinkToOutputStream. 

0 rows in set. Elapsed: 0.033 sec.
```

const String & name,
    WrittenStreams & written_streams)
{
    return [&] (const IDataType::SubstreamPath & path) -> WriteBuffer *
    {
        String stream_name = IDataType::getFileNameForStream(name, path);
        if (!written_streams.insert(stream_name).second)
            return nullptr;
        const auto & columns = metadata_snapshot->getColumns();
        if (!streams.count(stream_name))
            streams[stream_name] = std::make_unique<Stream>(
                storage.disk,
                storage.files[stream_name].data_file_path,
                columns.getCodecOrDefault(name),
                storage.max_compress_block_size);
        return &streams[stream_name]->compressed;
    };
}
void TinyLogBlockOutputStream::writeData(const String & name, const IDataType & type, const IColumn & column, WrittenStreams & written_streams)