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https://github.com/ClickHouse/ClickHouse.git
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329 lines
9.2 KiB
C++
329 lines
9.2 KiB
C++
#include <queue>
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#include <iomanip>
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#include <DB/DataStreams/MergingSortedBlockInputStream.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int LOGICAL_ERROR;
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extern const int NUMBER_OF_COLUMNS_DOESNT_MATCH;
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extern const int BLOCKS_HAS_DIFFERENT_STRUCTURE;
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}
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void MergingSortedBlockInputStream::init(Block & merged_block, ColumnPlainPtrs & merged_columns)
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{
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/// Читаем первые блоки, инициализируем очередь.
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if (first)
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{
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first = false;
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size_t i = 0;
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for (auto it = source_blocks.begin(); it != source_blocks.end(); ++it, ++i)
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{
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SharedBlockPtr & shared_block_ptr = *it;
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if (shared_block_ptr.get())
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continue;
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shared_block_ptr = new detail::SharedBlock(children[i]->read());
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const size_t rows = shared_block_ptr->rowsInFirstColumn();
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if (rows == 0)
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continue;
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if (!num_columns)
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num_columns = shared_block_ptr->columns();
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if (expected_block_size < rows)
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expected_block_size = std::min(rows, max_block_size);
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cursors[i] = SortCursorImpl(*shared_block_ptr, description, i);
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has_collation |= cursors[i].has_collation;
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}
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if (has_collation)
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initQueue(queue_with_collation);
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else
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initQueue(queue);
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}
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/// Инициализируем результат.
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/// Клонируем структуру первого непустого блока источников.
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{
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auto it = source_blocks.cbegin();
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for (; it != source_blocks.cend(); ++it)
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{
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const SharedBlockPtr & shared_block_ptr = *it;
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if (*shared_block_ptr)
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{
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merged_block = shared_block_ptr->cloneEmpty();
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break;
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}
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}
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/// Если все входные блоки пустые.
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if (it == source_blocks.cend())
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return;
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}
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/// Проверим, что у всех блоков-источников одинаковая структура.
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for (auto it = source_blocks.cbegin(); it != source_blocks.cend(); ++it)
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{
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const SharedBlockPtr & shared_block_ptr = *it;
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if (!*shared_block_ptr)
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continue;
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size_t src_columns = shared_block_ptr->columns();
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size_t dst_columns = merged_block.columns();
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if (src_columns != dst_columns)
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throw Exception("Merging blocks has different number of columns ("
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+ toString(src_columns) + " and " + toString(dst_columns) + ")",
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ErrorCodes::NUMBER_OF_COLUMNS_DOESNT_MATCH);
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for (size_t i = 0; i < src_columns; ++i)
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{
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if (shared_block_ptr->getByPosition(i).name != merged_block.getByPosition(i).name
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|| shared_block_ptr->getByPosition(i).type->getName() != merged_block.getByPosition(i).type->getName()
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|| shared_block_ptr->getByPosition(i).column->getName() != merged_block.getByPosition(i).column->getName())
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{
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throw Exception("Merging blocks has different names or types of columns:\n"
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+ shared_block_ptr->dumpStructure() + "\nand\n" + merged_block.dumpStructure(),
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ErrorCodes::BLOCKS_HAS_DIFFERENT_STRUCTURE);
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}
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}
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}
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for (size_t i = 0; i < num_columns; ++i)
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{
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merged_columns.emplace_back(merged_block.getByPosition(i).column.get());
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merged_columns.back()->reserve(expected_block_size);
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}
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}
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template <typename TSortCursor>
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void MergingSortedBlockInputStream::initQueue(std::priority_queue<TSortCursor> & queue)
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{
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for (size_t i = 0; i < cursors.size(); ++i)
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if (!cursors[i].empty())
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queue.push(TSortCursor(&cursors[i]));
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}
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Block MergingSortedBlockInputStream::readImpl()
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{
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if (finished)
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return Block();
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if (children.size() == 1)
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return children[0]->read();
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Block merged_block;
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ColumnPlainPtrs merged_columns;
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init(merged_block, merged_columns);
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if (merged_columns.empty())
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return Block();
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if (has_collation)
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merge(merged_block, merged_columns, queue_with_collation);
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else
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merge(merged_block, merged_columns, queue);
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return merged_block;
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}
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template <typename TSortCursor>
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void MergingSortedBlockInputStream::merge(Block & merged_block, ColumnPlainPtrs & merged_columns, std::priority_queue<TSortCursor> & queue)
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{
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size_t merged_rows = 0;
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/** Увеличить счётчики строк.
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* Вернуть true, если пора закончить формировать текущий блок данных.
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*/
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auto count_row_and_check_limit = [&, this]()
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{
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++total_merged_rows;
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if (limit && total_merged_rows == limit)
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{
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// std::cerr << "Limit reached\n";
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cancel();
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finished = true;
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return true;
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}
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++merged_rows;
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if (merged_rows == max_block_size)
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{
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// std::cerr << "max_block_size reached\n";
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return true;
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}
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return false;
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};
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/// Вынимаем строки в нужном порядке и кладём в merged_block, пока строк не больше max_block_size
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while (!queue.empty())
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{
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TSortCursor current = queue.top();
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queue.pop();
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while (true)
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{
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/** А вдруг для текущего курсора блок целиком меньше или равен, чем остальные?
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* Или в очереди остался только один источник данных? Тогда можно целиком взять блок текущего курсора.
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*/
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if (current.impl->isFirst() && (queue.empty() || current.totallyLessOrEquals(queue.top())))
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{
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// std::cerr << "current block is totally less or equals\n";
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/// Если в текущем блоке уже есть данные, то сначала вернём его. Мы попадём сюда снова при следующем вызове функции merge.
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if (merged_rows != 0)
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{
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// std::cerr << "merged rows is non-zero\n";
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queue.push(current);
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return;
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}
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/// Actually, current.impl->order stores source number (i.e. cursors[current.impl->order] == current.impl)
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size_t source_num = current.impl->order;
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if (source_num >= cursors.size())
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throw Exception("Logical error in MergingSortedBlockInputStream", ErrorCodes::LOGICAL_ERROR);
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for (size_t i = 0; i < num_columns; ++i)
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merged_block.unsafeGetByPosition(i).column = source_blocks[source_num]->unsafeGetByPosition(i).column;
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// std::cerr << "copied columns\n";
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size_t merged_rows = merged_block.rows();
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if (limit && total_merged_rows + merged_rows > limit)
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{
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merged_rows = limit - total_merged_rows;
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for (size_t i = 0; i < num_columns; ++i)
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{
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auto & column = merged_block.unsafeGetByPosition(i).column;
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column = column->cut(0, merged_rows);
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}
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cancel();
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finished = true;
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}
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if (out_row_sources)
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out_row_sources->resize_fill(out_row_sources->size() + merged_rows, RowSourcePart(source_num));
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// std::cerr << "fetching next block\n";
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total_merged_rows += merged_rows;
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fetchNextBlock(current, queue);
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return;
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}
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// std::cerr << "total_merged_rows: " << total_merged_rows << ", merged_rows: " << merged_rows << "\n";
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// std::cerr << "Inserting row\n";
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for (size_t i = 0; i < num_columns; ++i)
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merged_columns[i]->insertFrom(*current->all_columns[i], current->pos);
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if (out_row_sources)
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{
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/// Actually, current.impl->order stores source number (i.e. cursors[current.impl->order] == current.impl)
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out_row_sources->emplace_back(current.impl->order);
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}
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if (!current->isLast())
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{
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// std::cerr << "moving to next row\n";
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current->next();
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if (queue.empty() || !(current.greater(queue.top())))
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{
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if (count_row_and_check_limit())
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{
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// std::cerr << "pushing back to queue\n";
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queue.push(current);
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return;
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}
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/// Не кладём курсор обратно в очередь, а продолжаем работать с текущим курсором.
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// std::cerr << "current is still on top, using current row\n";
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continue;
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}
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else
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{
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// std::cerr << "next row is not least, pushing back to queue\n";
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queue.push(current);
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}
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}
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else
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{
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/// Достаём из соответствующего источника следующий блок, если есть.
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// std::cerr << "It was last row, fetching next block\n";
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fetchNextBlock(current, queue);
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}
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break;
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}
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if (count_row_and_check_limit())
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return;
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}
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cancel();
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finished = true;
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}
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template <typename TSortCursor>
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void MergingSortedBlockInputStream::fetchNextBlock(const TSortCursor & current, std::priority_queue<TSortCursor> & queue)
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{
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size_t i = 0;
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size_t size = cursors.size();
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for (; i < size; ++i)
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{
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if (&cursors[i] == current.impl)
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{
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source_blocks[i] = new detail::SharedBlock(children[i]->read());
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if (*source_blocks[i])
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{
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cursors[i].reset(*source_blocks[i]);
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queue.push(TSortCursor(&cursors[i]));
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}
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break;
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}
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}
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if (i == size)
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throw Exception("Logical error in MergingSortedBlockInputStream", ErrorCodes::LOGICAL_ERROR);
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}
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void MergingSortedBlockInputStream::readSuffixImpl()
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{
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/// Don't print performance info if Vertical algorithm is used
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if (out_row_sources)
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return;
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const BlockStreamProfileInfo & profile_info = getProfileInfo();
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double seconds = profile_info.total_stopwatch.elapsedSeconds();
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LOG_DEBUG(log, std::fixed << std::setprecision(2)
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<< "Merge sorted " << profile_info.blocks << " blocks, " << profile_info.rows << " rows"
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<< " in " << seconds << " sec., "
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<< profile_info.rows / seconds << " rows/sec., "
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<< profile_info.bytes / 1000000.0 / seconds << " MiB/sec.");
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}
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}
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