ClickHouse/dbms/DataStreams/ColumnGathererStream.cpp

#include <DataStreams/ColumnGathererStream.h>
#include <common/logger_useful.h>
#include <Common/typeid_cast.h>
#include <IO/WriteHelpers.h>
#include <iomanip>


namespace DB
{

namespace ErrorCodes
{
    extern const int INCOMPATIBLE_COLUMNS;
    extern const int INCORRECT_NUMBER_OF_COLUMNS;
    extern const int EMPTY_DATA_PASSED;
    extern const int RECEIVED_EMPTY_DATA;
}

ColumnGathererStream::ColumnGathererStream(
        const String & column_name_, const BlockInputStreams & source_streams, ReadBuffer & row_sources_buf_,
        size_t block_preferred_size_)
    : column_name(column_name_), sources(source_streams.size()), row_sources_buf(row_sources_buf_)
    , block_preferred_size(block_preferred_size_), log(&Logger::get("ColumnGathererStream"))
{
    if (source_streams.empty())
        throw Exception("There are no streams to gather", ErrorCodes::EMPTY_DATA_PASSED);

    children.assign(source_streams.begin(), source_streams.end());

    for (size_t i = 0; i < children.size(); ++i)
    {
        const Block & header = children[i]->getHeader();

        /// Sometimes MergeTreeReader injects additional column with partitioning key
        if (header.columns() > 2)
            throw Exception(
                "Block should have 1 or 2 columns, but contains " + toString(header.columns()),
                ErrorCodes::INCORRECT_NUMBER_OF_COLUMNS);

        if (i == 0)
        {
            column.name = column_name;
            column.type = header.getByName(column_name).type;
            column.column = column.type->createColumn();
        }
        else if (header.getByName(column_name).column->getName() != column.column->getName())
            throw Exception("Column types don't match", ErrorCodes::INCOMPATIBLE_COLUMNS);
    }
}


Block ColumnGathererStream::readImpl()
{
    /// Special case: single source and there are no skipped rows
    if (children.size() == 1 && row_sources_buf.eof())
        return children[0]->read();

    if (!source_to_fully_copy && row_sources_buf.eof())
        return Block();

    MutableColumnPtr output_column = column.column->cloneEmpty();
    output_block = Block{column.cloneEmpty()};
    output_column->gather(*this);
    if (!output_column->empty())
        output_block.getByPosition(0).column = std::move(output_column);
    return output_block;
}


void ColumnGathererStream::fetchNewBlock(Source & source, size_t source_num)
{
    try
    {
        source.block = children[source_num]->read();
        source.update(column_name);
    }
    catch (Exception & e)
    {
        e.addMessage("Cannot fetch required block. Stream " + children[source_num]->getName() + ", part " + toString(source_num));
        throw;
    }

    if (0 == source.size)
    {
        throw Exception("Fetched block is empty. Stream " + children[source_num]->getName() + ", part " + toString(source_num),
                        ErrorCodes::RECEIVED_EMPTY_DATA);
    }
}


void ColumnGathererStream::readSuffixImpl()
{
    const BlockStreamProfileInfo & profile_info = getProfileInfo();

    /// Don't print info for small parts (< 10M rows)
    if (profile_info.rows < 10000000)
        return;

    double seconds = profile_info.total_stopwatch.elapsedSeconds();

    std::stringstream message;
    message << std::fixed << std::setprecision(2)
        << "Gathered column " << column_name
        << " (" << static_cast<double>(profile_info.bytes) / profile_info.rows << " bytes/elem.)"
        << " in " << seconds << " sec.";

    if (seconds)
        message << ", " << profile_info.rows / seconds << " rows/sec., "
            << profile_info.bytes / 1048576.0 / seconds << " MiB/sec.";

    LOG_TRACE(log, message.str());
}

}