Function writeRemoteConvert

src/Storages/Distributed/DirectoryMonitor.cpp:308–354

    }

    void writeRemoteConvert(
        const DistributedHeader & distributed_header,
        RemoteBlockOutputStream & remote,
        bool compression_expected,
        ReadBufferFromFile & in,
        Poco::Logger * log)
    {
        if (!remote.getHeader())
        {
            CheckingCompressedReadBuffer checking_in(in);
            remote.writePrepared(checking_in);
            return;
        }

        /// This is old format, that does not have header for the block in the file header,
        /// applying ConvertingBlockInputStream in this case is not a big overhead.
        ///
        /// Anyway we can get header only from the first block, which contain all rows anyway.
        if (!distributed_header.block_header)
        {
            LOG_TRACE(log, "Processing batch {} with old format (no header)", in.getFileName());

            writeAndConvert(remote, in);
            return;
        }

        if (!blocksHaveEqualStructure(distributed_header.block_header, remote.getHeader()))
        {
            LOG_WARNING(log,
                "Structure does not match (remote: {}, local: {}), implicit conversion will be done",
                remote.getHeader().dumpStructure(), distributed_header.block_header.dumpStructure());

            writeAndConvert(remote, in);
            return;
        }

        /// If connection does not use compression, we have to uncompress the data.
        if (!compression_expected)
        {
            writeAndConvert(remote, in);
            return;
        }

        /// Otherwise write data as it was already prepared (more efficient path).
        CheckingCompressedReadBuffer checking_in(in);
        remote.writePrepared(checking_in);
    }
}