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

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#pragma once
#include <DB/Common/HashTable/HashMap.h>
#include <DB/Common/HashTable/ClearableHashSet.h>
template <typename Key, typename Mapped, typename Hash>
struct ClearableHashMapCell : public ClearableHashTableCell<Key, HashMapCell<Key, Mapped, Hash, ClearableHashSetState>>
{
using Base = ClearableHashTableCell<Key, HashMapCell<Key, Mapped, Hash, ClearableHashSetState>>;
using Base::Base;
ClearableHashMapCell(const typename Base::value_type & value_, const typename Base::State & state)
: Base::BaseCell(value_, state), Base::version(state.version) {}
};
template
<
typename Key,
typename Mapped,
typename Hash = DefaultHash<Key>,
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typename Grower = HashTableGrower<>,
typename Allocator = HashTableAllocator
>
class ClearableHashMap : public HashTable<Key, ClearableHashMapCell<Key, Mapped, Hash>, Hash, Grower, Allocator>
{
public:
using key_type = Key;
using mapped_type = Mapped;
using value_type = typename ClearableHashMap::cell_type::value_type;
mapped_type & operator[](Key x)
{
typename ClearableHashMap::iterator it;
bool inserted;
this->emplace(x, it, inserted);
if (inserted)
new(&it->second) mapped_type();
return it->second;
}
void clear()
{
++this->version;
this->m_size = 0;
}
};