ClickHouse/dbms/include/DB/Storages/MergeTree/MergeList.h

#pragma once

#include <DB/Common/Stopwatch.h>
#include <DB/Common/CurrentMetrics.h>
#include <DB/Common/MemoryTracker.h>
#include <DB/Interpreters/Context.h>
#include <memory>
#include <list>
#include <mutex>
#include <atomic>


/** Maintains a list of currently running merges.
  * For implementation of system.merges table.
  */

namespace CurrentMetrics
{
	extern const Metric Merge;
}

namespace DB
{


struct MergeInfo
{
	std::string database;
	std::string table;
	std::string result_part_name;
	Float64 elapsed;
	Float64 progress;
	UInt64 num_parts;
	UInt64 total_size_bytes_compressed;
	UInt64 total_size_marks;
	UInt64 bytes_read_uncompressed;
	UInt64 bytes_written_uncompressed;
	UInt64 rows_read;
	UInt64 rows_written;
	UInt64 columns_written;
	UInt64 memory_usage;
	UInt64 thread_number;
};


struct MergeListElement : boost::noncopyable
{
	const std::string database;
	const std::string table;
	const std::string result_part_name;
	Stopwatch watch;
	Float64 progress{};
	UInt64 num_parts{};
	UInt64 total_size_bytes_compressed{};
	UInt64 total_size_marks{};
	std::atomic<UInt64> bytes_read_uncompressed{};
	std::atomic<UInt64> bytes_written_uncompressed{};

	/// In case of Vertical algorithm they are actual only for primary key columns
	std::atomic<UInt64> rows_read{};
	std::atomic<UInt64> rows_written{};

	/// Updated only for Vertical algorithm
	std::atomic<UInt64> columns_written{};

	MemoryTracker memory_tracker;
	MemoryTracker * background_pool_task_memory_tracker;

	/// Poco thread number used in logs
	UInt32 thread_number;


	MergeListElement(const std::string & database, const std::string & table, const std::string & result_part_name);

	MergeInfo getInfo() const;

	~MergeListElement();
};


class MergeList;

class MergeListEntry
{
	MergeList & list;

	using container_t = std::list<MergeListElement>;
	container_t::iterator it;

	CurrentMetrics::Increment num_merges {CurrentMetrics::Merge};

public:
	MergeListEntry(const MergeListEntry &) = delete;
	MergeListEntry & operator=(const MergeListEntry &) = delete;

	MergeListEntry(MergeList & list, const container_t::iterator it) : list(list), it{it} {}
	~MergeListEntry();

	MergeListElement * operator->() { return &*it; }
};


class MergeList
{
	friend class MergeListEntry;

	using container_t = std::list<MergeListElement>;
	using info_container_t = std::list<MergeInfo>;

	mutable std::mutex mutex;
	container_t merges;

public:
	using Entry = MergeListEntry;
	using EntryPtr = std::unique_ptr<Entry>;

	template <typename... Args>
	EntryPtr insert(Args &&... args)
	{
		std::lock_guard<std::mutex> lock{mutex};
		return std::make_unique<Entry>(*this, merges.emplace(merges.end(), std::forward<Args>(args)...));
	}

	info_container_t get() const
	{
		std::lock_guard<std::mutex> lock{mutex};
		info_container_t res;
		for (const auto & merge_element : merges)
			res.emplace_back(merge_element.getInfo());
		return res;
	}
};


inline MergeListEntry::~MergeListEntry()
{
	std::lock_guard<std::mutex> lock{list.mutex};
	list.merges.erase(it);
}


}