Method readImpl

src/DataStreams/DistinctSortedBlockInputStream.cpp:21–78

}

Block DistinctSortedBlockInputStream::readImpl()
{
    /// Execute until end of stream or until
    /// a block with some new records will be gotten.
    for (;;)
    {
        /// Stop reading if we already reached the limit.
        if (limit_hint && data.getTotalRowCount() >= limit_hint)
            return Block();

        Block block = children.back()->read();
        if (!block)
            return Block();

        const ColumnRawPtrs column_ptrs(getKeyColumns(block));
        if (column_ptrs.empty())
            return block;

        const ColumnRawPtrs clearing_hint_columns(getClearingColumns(block, column_ptrs));

        if (data.type == ClearableSetVariants::Type::EMPTY)
            data.init(ClearableSetVariants::chooseMethod(column_ptrs, key_sizes));

        const size_t rows = block.rows();
        IColumn::Filter filter(rows);

        bool has_new_data = false;
        switch (data.type)
        {
            case ClearableSetVariants::Type::EMPTY:
                break;
            case ClearableSetVariants::Type::bitmap64:
                break;
    #define M(NAME) \
            case ClearableSetVariants::Type::NAME: \
                has_new_data = buildFilter(*data.NAME, column_ptrs, clearing_hint_columns, filter, rows, data); \
                break;
        APPLY_FOR_SET_VARIANTS(M)
    #undef M
        }

        /// Just go to the next block if there isn't any new record in the current one.
        if (!has_new_data)
            continue;

        if (!set_size_limits.check(data.getTotalRowCount(), data.getTotalByteCount(), "DISTINCT", ErrorCodes::SET_SIZE_LIMIT_EXCEEDED))
            return {};

        prev_block.block = block;
        prev_block.clearing_hint_columns = std::move(clearing_hint_columns);

        size_t all_columns = block.columns();
        for (size_t i = 0; i < all_columns; ++i)
            block.safeGetByPosition(i).column = block.safeGetByPosition(i).column->filter(filter, -1);

        return block;
    }
}