ClickHouse/dbms/include/DB/Storages/MergeTree/SimpleMergeSelector.h
2016-10-30 11:15:55 +03:00

39 lines
983 B
C++

#pragma once
#include <DB/Storages/MergeTree/MergeSelector.h>
namespace DB
{
class SimpleMergeSelector : public IMergeSelector
{
public:
struct Settings
{
/** Minimum ratio of size of one part to all parts in set of parts to merge (for usual cases).
* For example, if all parts have equal size, it means, that at least 'base' number of parts should be merged.
* If parts has non-uniform sizes, then minumum number of parts to merge is effectively increased.
* This behaviour balances merge-tree workload.
* It called 'base', because merge-tree depth could be estimated as logarithm with that base.
*/
double base = 8;
time_t lower_base_after = 300;
/// Zero means unlimited.
size_t max_parts_to_merge_at_once = 100;
};
SimpleMergeSelector(const Settings & settings) : settings(settings) {}
PartsInPartition select(
const Partitions & partitions,
const size_t max_total_size_to_merge) override;
private:
const Settings settings;
};
}