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45 lines
1.1 KiB
C++
45 lines
1.1 KiB
C++
#pragma once
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#include <DB/Storages/MergeTree/MergeSelector.h>
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namespace DB
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{
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/** Select parts to merge based on its level.
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*
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* Select first range of parts at least min_parts_to_merge length with minimum level.
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*
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* If enough time has passed, lower min_parts_to_merge.
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* And if no ranges of consecutive parts with same level, and much time has passed,
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* allow to select parts of different level.
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* This is done to allow further merging when table is not updated.
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*/
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class LevelMergeSelector : public IMergeSelector
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{
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public:
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struct Settings
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{
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size_t min_parts_to_merge = 8;
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size_t max_parts_to_merge = 100;
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/** min_parts_to_merge will be lowered by 1 after that time.
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* It will be lowered by 2 after that time * 2^1,
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* It will be lowered by 3 after that time * 2^2,
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* and so on, exponentially.
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*/
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time_t lower_base_after = 300;
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};
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LevelMergeSelector(const Settings & settings) : settings(settings) {}
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PartsInPartition select(
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const Partitions & partitions,
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const size_t max_total_size_to_merge) override;
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private:
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const Settings settings;
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};
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}
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