Function onWriteOrDeleteData

src/Databases/MySQL/MaterializeMySQLSyncThread.cpp:502–515

template <Int8 sign>
static size_t onWriteOrDeleteData(const Row & rows_data, Block & buffer)
{
    size_t prev_bytes = buffer.bytes();
    for (size_t column = 0; column < buffer.columns() - 1; ++column)
    {
        MutableColumnPtr col_to = IColumn::mutate(std::move(buffer.getByPosition(column).column));

        writeFieldsToColumn(*col_to, rows_data, column, {});
        buffer.getByPosition(column).column = std::move(col_to);
    }

    fillSignColumnsData(buffer, sign, rows_data.size());
    return buffer.bytes() - prev_bytes;
}

/// We need to use unique key instead of sorting key as user could use table override func
static inline bool differenceUniqueKeys(const Tuple & row_old_data, const Tuple & row_new_data, const std::vector<size_t> unique_columns_index)