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77 lines
1.8 KiB
C++
77 lines
1.8 KiB
C++
#include <Storages/MergeTree/MergeTreeReverseSelectProcessor.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 MEMORY_LIMIT_EXCEEDED;
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}
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bool MergeTreeReverseSelectProcessor::getNewTaskImpl()
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try
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{
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if (chunks.empty() && all_mark_ranges.empty())
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return false;
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/// We have some blocks to return in buffer.
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/// Return true to continue reading, but actually don't create a task.
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if (all_mark_ranges.empty())
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return true;
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if (!reader)
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initializeReaders();
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/// Read ranges from right to left.
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MarkRanges mark_ranges_for_task = { all_mark_ranges.back() };
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all_mark_ranges.pop_back();
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auto size_predictor = (preferred_block_size_bytes == 0) ? nullptr
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: getSizePredictor(data_part, task_columns, sample_block);
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task = std::make_unique<MergeTreeReadTask>(
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data_part, mark_ranges_for_task, part_index_in_query, ordered_names, column_name_set,
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task_columns, prewhere_info && prewhere_info->remove_prewhere_column,
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std::move(size_predictor));
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return true;
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}
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catch (...)
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{
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/// Suspicion of the broken part. A part is added to the queue for verification.
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if (getCurrentExceptionCode() != ErrorCodes::MEMORY_LIMIT_EXCEEDED)
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storage.reportBrokenPart(data_part);
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throw;
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}
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MergeTreeBaseSelectProcessor::BlockAndRowCount MergeTreeReverseSelectProcessor::readFromPart()
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{
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BlockAndRowCount res;
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if (!chunks.empty())
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{
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res = std::move(chunks.back());
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chunks.pop_back();
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return res;
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}
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if (!task->range_reader.isInitialized())
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initializeRangeReaders(*task);
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while (!task->isFinished())
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{
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auto chunk = readFromPartImpl();
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chunks.push_back(std::move(chunk));
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}
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if (chunks.empty())
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return {};
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res = std::move(chunks.back());
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chunks.pop_back();
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return res;
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}
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}
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