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242 lines
8.7 KiB
C++
242 lines
8.7 KiB
C++
#pragma once
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#include <Common/HashTable/Hash.h>
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#include <Common/HashTable/HashTable.h>
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#include <Common/HashTable/HashTableAllocator.h>
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/** NOTE HashMap could only be used for memmoveable (position independent) types.
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* Example: std::string is not position independent in libstdc++ with C++11 ABI or in libc++.
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* Also, key in hash table must be of type, that zero bytes is compared equals to zero key.
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*/
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struct NoInitTag
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{
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};
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/// A pair that does not initialize the elements, if not needed.
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template <typename First, typename Second>
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struct PairNoInit
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{
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First first;
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Second second;
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PairNoInit() {}
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template <typename First_>
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PairNoInit(First_ && first_, NoInitTag) : first(std::forward<First_>(first_))
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{
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}
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template <typename First_, typename Second_>
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PairNoInit(First_ && first_, Second_ && second_) : first(std::forward<First_>(first_)), second(std::forward<Second_>(second_))
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{
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}
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};
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template <typename Key, typename TMapped, typename Hash, typename TState = HashTableNoState>
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struct HashMapCell
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{
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using Mapped = TMapped;
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using State = TState;
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using value_type = PairNoInit<Key, Mapped>;
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using mapped_type = Mapped;
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using key_type = Key;
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value_type value;
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HashMapCell() {}
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HashMapCell(const Key & key_, const State &) : value(key_, NoInitTag()) {}
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HashMapCell(const value_type & value_, const State &) : value(value_) {}
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/// Get the key (externally).
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const Key & getKey() const { return value.first; }
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Mapped & getMapped() { return value.second; }
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const Mapped & getMapped() const { return value.second; }
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const value_type & getValue() const { return value; }
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/// Get the key (internally).
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static const Key & getKey(const value_type & value) { return value.first; }
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bool keyEquals(const Key & key_) const { return value.first == key_; }
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bool keyEquals(const Key & key_, size_t /*hash_*/) const { return value.first == key_; }
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bool keyEquals(const Key & key_, size_t /*hash_*/, const State & /*state*/) const { return value.first == key_; }
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void setHash(size_t /*hash_value*/) {}
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size_t getHash(const Hash & hash) const { return hash(value.first); }
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bool isZero(const State & state) const { return isZero(value.first, state); }
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static bool isZero(const Key & key, const State & /*state*/) { return ZeroTraits::check(key); }
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/// Set the key value to zero.
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void setZero() { ZeroTraits::set(value.first); }
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/// Do I need to store the zero key separately (that is, can a zero key be inserted into the hash table).
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static constexpr bool need_zero_value_storage = true;
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/// Whether the cell was deleted.
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bool isDeleted() const { return false; }
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void setMapped(const value_type & value_) { value.second = value_.second; }
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/// Serialization, in binary and text form.
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void write(DB::WriteBuffer & wb) const
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{
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DB::writeBinary(value.first, wb);
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DB::writeBinary(value.second, wb);
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}
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void writeText(DB::WriteBuffer & wb) const
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{
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DB::writeDoubleQuoted(value.first, wb);
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DB::writeChar(',', wb);
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DB::writeDoubleQuoted(value.second, wb);
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}
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/// Deserialization, in binary and text form.
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void read(DB::ReadBuffer & rb)
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{
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DB::readBinary(value.first, rb);
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DB::readBinary(value.second, rb);
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}
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void readText(DB::ReadBuffer & rb)
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{
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DB::readDoubleQuoted(value.first, rb);
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DB::assertChar(',', rb);
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DB::readDoubleQuoted(value.second, rb);
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}
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};
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template <typename Key, typename TMapped, typename Hash, typename TState = HashTableNoState>
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struct HashMapCellWithSavedHash : public HashMapCell<Key, TMapped, Hash, TState>
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{
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using Base = HashMapCell<Key, TMapped, Hash, TState>;
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size_t saved_hash;
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using Base::Base;
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bool keyEquals(const Key & key_) const { return this->value.first == key_; }
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bool keyEquals(const Key & key_, size_t hash_) const { return saved_hash == hash_ && this->value.first == key_; }
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bool keyEquals(const Key & key_, size_t hash_, const typename Base::State &) const { return keyEquals(key_, hash_); }
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void setHash(size_t hash_value) { saved_hash = hash_value; }
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size_t getHash(const Hash & /*hash_function*/) const { return saved_hash; }
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};
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template <
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typename Key,
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typename Cell,
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typename Hash = DefaultHash<Key>,
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typename Grower = HashTableGrower<>,
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typename Allocator = HashTableAllocator>
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class HashMapTable : public HashTable<Key, Cell, Hash, Grower, Allocator>
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{
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public:
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using Self = HashMapTable;
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using Base = HashTable<Key, Cell, Hash, Grower, Allocator>;
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using LookupResult = typename Base::LookupResult;
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using Base::Base;
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/// Merge every cell's value of current map into the destination map via emplace.
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/// Func should have signature void(Mapped & dst, Mapped & src, bool emplaced).
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/// Each filled cell in current map will invoke func once. If that map doesn't
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/// have a key equals to the given cell, a new cell gets emplaced into that map,
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/// and func is invoked with the third argument emplaced set to true. Otherwise
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/// emplaced is set to false.
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template <typename Func>
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void ALWAYS_INLINE mergeToViaEmplace(Self & that, Func && func)
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{
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for (auto it = this->begin(), end = this->end(); it != end; ++it)
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{
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typename Self::LookupResult res_it;
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bool inserted;
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that.emplace(Cell::getKey(it->getValue()), res_it, inserted, it.getHash());
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func(res_it->getMapped(), it->getMapped(), inserted);
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}
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}
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/// Merge every cell's value of current map into the destination map via find.
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/// Func should have signature void(Mapped & dst, Mapped & src, bool exist).
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/// Each filled cell in current map will invoke func once. If that map doesn't
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/// have a key equals to the given cell, func is invoked with the third argument
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/// exist set to false. Otherwise exist is set to true.
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template <typename Func>
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void ALWAYS_INLINE mergeToViaFind(Self & that, Func && func)
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{
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for (auto it = this->begin(), end = this->end(); it != end; ++it)
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{
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auto res_it = that.find(Cell::getKey(it->getValue()), it.getHash());
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if (!res_it)
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func(it->getMapped(), it->getMapped(), false);
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else
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func(res_it->getMapped(), it->getMapped(), true);
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}
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}
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/// Call func(const Key &, Mapped &) for each hash map element.
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template <typename Func>
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void forEachValue(Func && func)
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{
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for (auto & v : *this)
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func(v.getKey(), v.getMapped());
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}
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/// Call func(Mapped &) for each hash map element.
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template <typename Func>
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void forEachMapped(Func && func)
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{
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for (auto & v : *this)
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func(v.getMapped());
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}
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typename Cell::Mapped & ALWAYS_INLINE operator[](const Key & x)
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{
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LookupResult it;
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bool inserted;
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this->emplace(x, it, inserted);
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/** It may seem that initialization is not necessary for POD-types (or __has_trivial_constructor),
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* since the hash table memory is initially initialized with zeros.
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* But, in fact, an empty cell may not be initialized with zeros in the following cases:
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* - ZeroValueStorage (it only zeros the key);
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* - after resizing and moving a part of the cells to the new half of the hash table, the old cells also have only the key to zero.
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*
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* On performance, there is almost always no difference, due to the fact that it->second is usually assigned immediately
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* after calling `operator[]`, and since `operator[]` is inlined, the compiler removes unnecessary initialization.
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*
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* Sometimes due to initialization, the performance even grows. This occurs in code like `++map[key]`.
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* When we do the initialization, for new cells, it's enough to make `store 1` right away.
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* And if we did not initialize, then even though there was zero in the cell,
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* the compiler can not guess about this, and generates the `load`, `increment`, `store` code.
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*/
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if (inserted)
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new (&it->getMapped()) typename Cell::Mapped();
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return it->getMapped();
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}
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};
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template <
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typename Key,
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typename Mapped,
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typename Hash = DefaultHash<Key>,
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typename Grower = HashTableGrower<>,
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typename Allocator = HashTableAllocator>
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using HashMap = HashMapTable<Key, HashMapCell<Key, Mapped, Hash>, Hash, Grower, Allocator>;
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template <
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typename Key,
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typename Mapped,
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typename Hash = DefaultHash<Key>,
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typename Grower = HashTableGrower<>,
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typename Allocator = HashTableAllocator>
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using HashMapWithSavedHash = HashMapTable<Key, HashMapCellWithSavedHash<Key, Mapped, Hash>, Hash, Grower, Allocator>;
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