Method write

src/DataStreams/NativeBlockOutputStream.cpp:104–176

void NativeBlockOutputStream::write(const Block & block)
{
    /// Additional information about the block.
    if (client_revision > 0)
        block.info.write(ostr);

    block.checkNumberOfRows();

    /// Dimensions
    size_t columns = block.columns();
    size_t rows = block.rows();

    writeVarUInt(columns, ostr);
    writeVarUInt(rows, ostr);

    /** The index has the same structure as the data stream.
      * But instead of column values, it contains a mark that points to the location in the data file where this part of the column is located.
      */
    if (index_ostr)
    {
        writeVarUInt(columns, *index_ostr);
        writeVarUInt(rows, *index_ostr);
    }

    for (size_t i = 0; i < columns; ++i)
    {
        /// For the index.
        MarkInCompressedFile mark;

        if (index_ostr)
        {
            ostr_concrete->next();  /// Finish compressed block.
            mark.offset_in_compressed_file = initial_size_of_file + ostr_concrete->getCompressedBytes();
            mark.offset_in_decompressed_block = ostr_concrete->getRemainingBytes();
        }

        ColumnWithTypeAndName column = block.safeGetByPosition(i);

        /// Send data to old clients without low cardinality type.
        if (remove_low_cardinality || (client_revision && client_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE))
        {
            column.column = recursiveRemoveLowCardinality(column.column);
            column.type = recursiveRemoveLowCardinality(column.type);
        }

        /// Name
        writeStringBinary(column.name, ostr);

        /// Type
        String type_name = column.type->getName();

        /// For compatibility, we will not send explicit timezone parameter in DateTime data type
        ///  to older clients, that cannot understand it.
        if (client_revision < DBMS_MIN_REVISION_WITH_TIME_ZONE_PARAMETER_IN_DATETIME_DATA_TYPE
            && startsWith(type_name, "DateTime("))
            type_name = "DateTime";

        writeStringBinary(type_name, ostr);