Function convertColumnsToNullable

src/Interpreters/join_common.cpp:157–161

}

void convertColumnsToNullable(Block & block, size_t starting_pos)
{
    for (size_t i = starting_pos; i < block.columns(); ++i)
        convertColumnToNullable(block.getByPosition(i));
}

/// Convert column to nullable. If column LowCardinality or Const, convert nested column.
/// Returns nullptr if conversion cannot be performed.