mirror of
https://github.com/ClickHouse/ClickHouse.git
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142 lines
3.2 KiB
C++
142 lines
3.2 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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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 (Blocks::iterator it = source_blocks.begin(); it != source_blocks.end(); ++it, ++i)
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{
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if (*it)
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continue;
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*it = inputs[i]->read();
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if (!*it)
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continue;
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if (!num_columns)
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num_columns = source_blocks[0].columns();
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cursors[i] = SortCursorImpl(*it, description, i);
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queue.push(SortCursor(&cursors[i]));
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}
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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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Blocks::const_iterator it = source_blocks.begin();
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for (; it != source_blocks.end(); ++it)
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{
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if (*it)
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{
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merged_block = it->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.end())
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return;
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}
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for (size_t i = 0; i < num_columns; ++i)
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merged_columns.push_back(&*merged_block.getByPosition(i).column);
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}
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Block MergingSortedBlockInputStream::readImpl()
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{
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if (!inputs.size())
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return Block();
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if (inputs.size() == 1)
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return inputs[0]->read();
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size_t merged_rows = 0;
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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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/// 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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SortCursor current = queue.top();
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queue.pop();
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for (size_t i = 0; i < num_columns; ++i)
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merged_columns[i]->insert((*current->all_columns[i])[current->pos]);
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if (!current->isLast())
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{
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current->next();
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queue.push(current);
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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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fetchNextBlock(current);
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}
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++merged_rows;
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if (merged_rows == max_block_size)
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return merged_block;
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}
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inputs.clear();
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return merged_block;
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}
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void MergingSortedBlockInputStream::fetchNextBlock(const SortCursor & current)
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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] = inputs[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(SortCursor(&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::readSuffix()
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{
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const BlockStreamProfileInfo & profile_info = getInfo();
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double seconds = profile_info.work_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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