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36 lines
847 B
C++
36 lines
847 B
C++
#include <random>
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#include <Common/thread_local_rng.h>
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#include <DataStreams/ConcatBlockInputStream.h>
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namespace DB
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{
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BlockInputStreams narrowBlockInputStreams(BlockInputStreams & inputs, size_t width)
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{
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size_t size = inputs.size();
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if (size <= width)
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return inputs;
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std::vector<BlockInputStreams> partitions(width);
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using Distribution = std::vector<size_t>;
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Distribution distribution(size);
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for (size_t i = 0; i < size; ++i)
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distribution[i] = i % width;
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std::shuffle(distribution.begin(), distribution.end(), thread_local_rng);
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for (size_t i = 0; i < size; ++i)
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partitions[distribution[i]].push_back(inputs[i]);
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BlockInputStreams res(width);
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for (size_t i = 0; i < width; ++i)
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res[i] = std::make_shared<ConcatBlockInputStream>(partitions[i]);
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return res;
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}
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}
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