void MergingSortedBlockInputStream::merge(Block & merged_block, ColumnPlainPtrs & merged_columns, std::priority_queue<TSortCursor> & queue)
{
size_t merged_rows = 0;
/** Увеличить счётчики строк.
* Вернуть true, если пора закончить формировать текущий блок данных.
*/
auto count_row_and_check_limit = [&, this]()
{
++total_merged_rows;
if (limit && total_merged_rows == limit)
{
// std::cerr << "Limit reached\n";
cancel();
finished = true;
return true;
}
++merged_rows;
if (merged_rows == max_block_size)
{
// std::cerr << "max_block_size reached\n";
return true;
}
return false;
};
/// Вынимаем строки в нужном порядке и кладём в merged_block, пока строк не больше max_block_size
while (!queue.empty())
{
TSortCursor current = queue.top();
queue.pop();
while (true)
{
/** А вдруг для текущего курсора блок целиком меньше или равен, чем остальные?
* Или в очереди остался только один источник данных? Тогда можно целиком взять блок текущего курсора.
*/
if (current.impl->isFirst() && (queue.empty() || current.totallyLessOrEquals(queue.top())))
{
// std::cerr << "current block is totally less or equals\n";
/// Если в текущем блоке уже есть данные, то сначала вернём его. Мы попадём сюда снова при следующем вызове функции merge.
if (merged_rows != 0)
{
// std::cerr << "merged rows is non-zero\n";
queue.push(current);
return;
}
size_t source_num = 0;
size_t size = cursors.size();
for (; source_num < size; ++source_num)
if (&cursors[source_num] == current.impl)
break;
if (source_num == size)
throw Exception("Logical error in MergingSortedBlockInputStream", ErrorCodes::LOGICAL_ERROR);
for (size_t i = 0; i < num_columns; ++i)
merged_block.unsafeGetByPosition(i).column = source_blocks[source_num]->unsafeGetByPosition(i).column;
// std::cerr << "copied columns\n";
size_t merged_rows = merged_block.rows();
if (limit && total_merged_rows + merged_rows > limit)
{
merged_rows = limit - total_merged_rows;
for (size_t i = 0; i < num_columns; ++i)
{
auto & column = merged_block.unsafeGetByPosition(i).column;
column = column->cut(0, merged_rows);
}
cancel();
finished = true;
}
// std::cerr << "fetching next block\n";
total_merged_rows += merged_rows;
fetchNextBlock(current, queue);
return;
}
// std::cerr << "total_merged_rows: " << total_merged_rows << ", merged_rows: " << merged_rows << "\n";
// std::cerr << "Inserting row\n";
for (size_t i = 0; i < num_columns; ++i)
merged_columns[i]->insertFrom(*current->all_columns[i], current->pos);
if (!current->isLast())
{
// std::cerr << "moving to next row\n";
current->next();
if (queue.empty() || !(current.greater(queue.top())))
{
if (count_row_and_check_limit())
{
// std::cerr << "pushing back to queue\n";
queue.push(current);
return;
}
/// Не кладём курсор обратно в очередь, а продолжаем работать с текущим курсором.
// std::cerr << "current is still on top, using current row\n";
continue;
}
else
{
// std::cerr << "next row is not least, pushing back to queue\n";
queue.push(current);
}
}
else
{
/// Достаём из соответствующего источника следующий блок, если есть.
// std::cerr << "It was last row, fetching next block\n";
fetchNextBlock(current, queue);
}
break;
}
if (count_row_and_check_limit())
return;
}
cancel();
finished = true;
}
void AggregatingSortedBlockInputStream::merge(ColumnPlainPtrs & merged_columns, std::priority_queue<TSortCursor> & queue)
{
size_t merged_rows = 0;
/// Вынимаем строки в нужном порядке и кладём в merged_block, пока строк не больше max_block_size
while (!queue.empty())
{
TSortCursor current = queue.top();
setPrimaryKeyRef(next_key, current);
bool key_differs;
if (current_key.empty()) /// Первый встретившийся ключ.
{
current_key.columns.resize(description.size());
setPrimaryKeyRef(current_key, current);
key_differs = true;
}
else
key_differs = next_key != current_key;
/// если накопилось достаточно строк и последняя посчитана полностью
if (key_differs && merged_rows >= max_block_size)
return;
queue.pop();
if (key_differs)
{
current_key.swap(next_key);
/// Запишем данные для очередной группы. Копируем значения обычных столбцов.
for (size_t i = 0, size = column_numbers_not_to_aggregate.size(); i < size; ++i)
{
size_t j = column_numbers_not_to_aggregate[i];
merged_columns[j]->insertFrom(*current->all_columns[j], current->pos);
}
/// Добавляем в агрегатные столбцы пустое состояние агрегации. Состояние будет обновлено в функции addRow.
for (auto & column_to_aggregate : columns_to_aggregate)
column_to_aggregate->insertDefault();
++merged_rows;
}
addRow(current);
if (!current->isLast())
{
current->next();
queue.push(current);
}
else
{
/// Достаём из соответствующего источника следующий блок, если есть.
fetchNextBlock(current, queue);
}
}
finished = true;
}
void AggregatingSortedBlockInputStream::merge(MutableColumns & merged_columns, std::priority_queue<SortCursor> & queue)
{
size_t merged_rows = 0;
/// We take the rows in the correct order and put them in `merged_block`, while the rows are no more than `max_block_size`
while (!queue.empty())
{
SortCursor current = queue.top();
setPrimaryKeyRef(next_key, current);
bool key_differs;
if (current_key.empty()) /// The first key encountered.
{
setPrimaryKeyRef(current_key, current);
key_differs = true;
}
else
key_differs = next_key != current_key;
/// if there are enough rows accumulated and the last one is calculated completely
if (key_differs && merged_rows >= max_block_size)
return;
queue.pop();
if (key_differs)
{
current_key.swap(next_key);
/// We will write the data for the group. We copy the values of ordinary columns.
for (size_t i = 0, size = column_numbers_not_to_aggregate.size(); i < size; ++i)
{
size_t j = column_numbers_not_to_aggregate[i];
merged_columns[j]->insertFrom(*current->all_columns[j], current->pos);
}
/// Add the empty aggregation state to the aggregate columns. The state will be updated in the `addRow` function.
for (auto & column_to_aggregate : columns_to_aggregate)
column_to_aggregate->insertDefault();
++merged_rows;
}
addRow(current);
if (!current->isLast())
{
current->next();
queue.push(current);
}
else
{
/// We fetch the next block from the appropriate source, if there is one.
fetchNextBlock(current, queue);
}
}
finished = true;
}
void MergingSortedBlockInputStream::merge(MutableColumns & merged_columns, std::priority_queue<TSortCursor> & queue)
{
size_t merged_rows = 0;
/** Increase row counters.
* Return true if it's time to finish generating the current data block.
*/
auto count_row_and_check_limit = [&, this]()
{
++total_merged_rows;
if (limit && total_merged_rows == limit)
{
// std::cerr << "Limit reached\n";
cancel(false);
finished = true;
return true;
}
++merged_rows;
if (merged_rows == max_block_size)
{
// std::cerr << "max_block_size reached\n";
return true;
}
return false;
};
/// Take rows in required order and put them into `merged_columns`, while the rows are no more than `max_block_size`
while (!queue.empty())
{
TSortCursor current = queue.top();
queue.pop();
while (true)
{
/** And what if the block is totally less or equal than the rest for the current cursor?
* Or is there only one data source left in the queue? Then you can take the entire block on current cursor.
*/
if (current.impl->isFirst() && (queue.empty() || current.totallyLessOrEquals(queue.top())))
{
// std::cerr << "current block is totally less or equals\n";
/// If there are already data in the current block, we first return it. We'll get here again the next time we call the merge function.
if (merged_rows != 0)
{
// std::cerr << "merged rows is non-zero\n";
queue.push(current);
return;
}
/// Actually, current.impl->order stores source number (i.e. cursors[current.impl->order] == current.impl)
size_t source_num = current.impl->order;
if (source_num >= cursors.size())
throw Exception("Logical error in MergingSortedBlockInputStream", ErrorCodes::LOGICAL_ERROR);
for (size_t i = 0; i < num_columns; ++i)
merged_columns[i] = (*std::move(source_blocks[source_num]->getByPosition(i).column)).mutate();
// std::cerr << "copied columns\n";
merged_rows = merged_columns.at(0)->size();
if (limit && total_merged_rows + merged_rows > limit)
{
merged_rows = limit - total_merged_rows;
for (size_t i = 0; i < num_columns; ++i)
{
auto & column = merged_columns[i];
column = (*column->cut(0, merged_rows)).mutate();
}
cancel(false);
finished = true;
}
if (out_row_sources_buf)
{
RowSourcePart row_source(source_num);
for (size_t i = 0; i < merged_rows; ++i)
out_row_sources_buf->write(row_source.data);
}
// std::cerr << "fetching next block\n";
total_merged_rows += merged_rows;
fetchNextBlock(current, queue);
return;
}
// std::cerr << "total_merged_rows: " << total_merged_rows << ", merged_rows: " << merged_rows << "\n";
// std::cerr << "Inserting row\n";
for (size_t i = 0; i < num_columns; ++i)
merged_columns[i]->insertFrom(*current->all_columns[i], current->pos);
if (out_row_sources_buf)
{
/// Actually, current.impl->order stores source number (i.e. cursors[current.impl->order] == current.impl)
RowSourcePart row_source(current.impl->order);
out_row_sources_buf->write(row_source.data);
}
if (!current->isLast())
{
// std::cerr << "moving to next row\n";
current->next();
if (queue.empty() || !(current.greater(queue.top())))
{
if (count_row_and_check_limit())
{
// std::cerr << "pushing back to queue\n";
queue.push(current);
return;
}
/// Do not put the cursor back in the queue, but continue to work with the current cursor.
// std::cerr << "current is still on top, using current row\n";
continue;
}
else
{
// std::cerr << "next row is not least, pushing back to queue\n";
queue.push(current);
}
}
else
{
/// We get the next block from the corresponding source, if there is one.
// std::cerr << "It was last row, fetching next block\n";
fetchNextBlock(current, queue);
}
break;
}
if (count_row_and_check_limit())
return;
}
cancel(false);
finished = true;
}
