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64 lines
1.7 KiB
C++
64 lines
1.7 KiB
C++
#pragma once
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#include <queue>
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#include <Yandex/logger_useful.h>
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#include <DB/Core/SortDescription.h>
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#include <DB/DataStreams/IProfilingBlockInputStream.h>
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namespace DB
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{
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/** Соединяет несколько сортированных потоков в один.
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*/
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class MergingSortedBlockInputStream : public IProfilingBlockInputStream
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{
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public:
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MergingSortedBlockInputStream(BlockInputStreams inputs_, SortDescription & description_, size_t max_block_size_)
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: inputs(inputs_), description(description_), max_block_size(max_block_size_), first(true),
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num_columns(0), source_blocks(inputs.size()), cursors(inputs.size()), log(&Logger::get("MergingSortedBlockInputStream"))
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{
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children.insert(children.end(), inputs.begin(), inputs.end());
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}
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void readSuffix();
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String getName() const { return "MergingSortedBlockInputStream"; }
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BlockInputStreamPtr clone() { return new MergingSortedBlockInputStream(inputs, description, max_block_size); }
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protected:
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Block readImpl();
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/// Инициализирует очередь и следующий блок результата.
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void init(Block & merged_block, ColumnPlainPtrs & merged_columns);
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/// Достаёт из источника, соответствующего current следующий блок.
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void fetchNextBlock(const SortCursor & current);
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BlockInputStreams inputs;
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SortDescription description;
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size_t max_block_size;
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bool first;
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/// Текущие сливаемые блоки.
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size_t num_columns;
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Blocks source_blocks;
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typedef std::vector<SortCursorImpl> CursorImpls;
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CursorImpls cursors;
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typedef std::priority_queue<SortCursor> Queue;
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Queue queue;
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private:
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Logger * log;
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};
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}
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