Method updateExtremes

src/DataStreams/IBlockInputStream.cpp:189–252

void IBlockInputStream::updateExtremes(Block & block)
{
    size_t num_columns = block.columns();

    if (!extremes)
    {
        MutableColumns extremes_columns(num_columns);

        for (size_t i = 0; i < num_columns; ++i)
        {
            const ColumnPtr & src = block.safeGetByPosition(i).column;

            if (isColumnConst(*src))
            {
                /// Equal min and max.
                extremes_columns[i] = src->cloneResized(2);
            }
            else
            {
                Field min_value;
                Field max_value;

                src->getExtremes(min_value, max_value);

                extremes_columns[i] = src->cloneEmpty();

                extremes_columns[i]->insert(min_value);
                extremes_columns[i]->insert(max_value);
            }
        }

        extremes = block.cloneWithColumns(std::move(extremes_columns));
    }
    else
    {
        for (size_t i = 0; i < num_columns; ++i)
        {
            ColumnPtr & old_extremes = extremes.safeGetByPosition(i).column;

            if (isColumnConst(*old_extremes))
                continue;

            Field min_value = (*old_extremes)[0];
            Field max_value = (*old_extremes)[1];

            Field cur_min_value;
            Field cur_max_value;

            block.safeGetByPosition(i).column->getExtremes(cur_min_value, cur_max_value);

            if (cur_min_value < min_value)
                min_value = cur_min_value;
            if (cur_max_value > max_value)
                max_value = cur_max_value;

            MutableColumnPtr new_extremes = old_extremes->cloneEmpty();

            new_extremes->insert(min_value);