ClickHouse/dbms/include/DB/Common/HashTable/HashSet.h

#pragma once

#include <DB/Common/HashTable/Hash.h>
#include <DB/Common/HashTable/HashTable.h>
#include <DB/Common/HashTable/HashTableAllocator.h>

#include <DB/IO/WriteBuffer.h>
#include <DB/IO/WriteHelpers.h>
#include <DB/IO/ReadBuffer.h>
#include <DB/IO/ReadHelpers.h>
#include <DB/IO/VarInt.h>


template
<
	typename Key,
	typename TCell,
	typename Hash = DefaultHash<Key>,
	typename Grower = HashTableGrower<>,
	typename Allocator = HashTableAllocator
>
class HashSetTable : public HashTable<Key, TCell, Hash, Grower, Allocator>
{
public:
	typedef HashSetTable<Key, TCell, Hash, Grower, Allocator> Self;
	typedef TCell Cell;

	void merge(const Self & rhs)
	{
		if (!this->hasZero() && rhs.hasZero())
		{
			this->setHasZero();
			++this->m_size;
		}

		for (size_t i = 0; i < rhs.grower.bufSize(); ++i)
			if (!rhs.buf[i].isZero(*this))
				this->insert(Cell::getKey(rhs.buf[i].getValue()));
	}


	void readAndMerge(DB::ReadBuffer & rb)
	{
		Cell::State::read(rb);

		size_t new_size = 0;
		DB::readVarUInt(new_size, rb);

		this->resize(new_size);

		for (size_t i = 0; i < new_size; ++i)
		{
			Cell x;
			x.read(rb);
			this->insert(Cell::getKey(x.getValue()));
		}
	}
};


template <typename Key, typename Hash, typename TState = HashTableNoState>
struct HashSetCellWithSavedHash : public HashTableCell<Key, Hash, TState>
{
	typedef HashTableCell<Key, Hash, TState> Base;

	size_t saved_hash;

	HashSetCellWithSavedHash() : Base() {}
	HashSetCellWithSavedHash(const Key & key_, const typename Base::State & state) : Base(key_, state) {}

	bool keyEquals(const Key & key_) const { return this->key == key_; }
	bool keyEquals(const HashSetCellWithSavedHash & other) const { return saved_hash == other.saved_hash && this->key == other.key; }

	void setHash(size_t hash_value) { saved_hash = hash_value; }
	size_t getHash(const Hash & hash) const { return saved_hash; }
};


template
<
	typename Key,
	typename Hash = DefaultHash<Key>,
	typename Grower = HashTableGrower<>,
	typename Allocator = HashTableAllocator
>
using HashSet = HashSetTable<Key, HashTableCell<Key, Hash>, Hash, Grower, Allocator>;


template
<
	typename Key,
	typename Hash = DefaultHash<Key>,
	typename Grower = HashTableGrower<>,
	typename Allocator = HashTableAllocator
>
using HashSetWithSavedHash = HashSetTable<Key, HashSetCellWithSavedHash<Key, Hash>, Hash, Grower, Allocator>;