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https://github.com/ClickHouse/ClickHouse.git
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420 lines
12 KiB
C++
420 lines
12 KiB
C++
#pragma once
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#include <Common/HashTable/HashTable.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int NO_AVAILABLE_DATA;
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}
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}
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template <typename Key, typename TState = HashTableNoState>
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struct FixedHashTableCell
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{
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using State = TState;
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using value_type = Key;
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using mapped_type = VoidMapped;
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bool full;
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FixedHashTableCell() {}
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FixedHashTableCell(const Key &, const State &) : full(true) {}
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const VoidKey getKey() const { return {}; }
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VoidMapped getMapped() const { return {}; }
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bool isZero(const State &) const { return !full; }
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void setZero() { full = false; }
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static constexpr bool need_zero_value_storage = false;
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/// This Cell is only stored inside an iterator. It's used to accomodate the fact
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/// that the iterator based API always provide a reference to a continuous memory
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/// containing the Key. As a result, we have to instantiate a real Key field.
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/// All methods that return a mutable reference to the Key field are named with
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/// -Mutable suffix, indicating this is uncommon usage. As this is only for lookup
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/// tables, it's totally fine to discard the Key mutations.
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struct CellExt
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{
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Key key;
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const VoidKey getKey() const { return {}; }
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VoidMapped getMapped() const { return {}; }
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const value_type & getValue() const { return key; }
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void update(Key && key_, FixedHashTableCell *) { key = key_; }
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};
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};
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/** Used as a lookup table for small keys such as UInt8, UInt16. It's different
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* than a HashTable in that keys are not stored in the Cell buf, but inferred
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* inside each iterator. There are a bunch of to make it faster than using
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* HashTable: a) It doesn't have a conflict chain; b) There is no key
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* comparision; c) The number of cycles for checking cell empty is halved; d)
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* Memory layout is tighter, especially the Clearable variants.
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*
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* NOTE: For Set variants this should always be better. For Map variants
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* however, as we need to assemble the real cell inside each iterator, there
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* might be some cases we fall short.
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*
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* TODO: Deprecate the cell API so that end users don't rely on the structure
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* of cell. Instead iterator should be used for operations such as cell
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* transfer, key updates (f.g. StringRef) and serde. This will allow
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* TwoLevelHashSet(Map) to contain different type of sets(maps).
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*/
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template <typename Key, typename Cell, typename Allocator>
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class FixedHashTable : private boost::noncopyable, protected Allocator, protected Cell::State
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{
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static constexpr size_t NUM_CELLS = 1ULL << (sizeof(Key) * 8);
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protected:
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friend class const_iterator;
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friend class iterator;
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friend class Reader;
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using Self = FixedHashTable;
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size_t m_size = 0; /// Amount of elements
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Cell * buf; /// A piece of memory for all elements.
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void alloc() { buf = reinterpret_cast<Cell *>(Allocator::alloc(NUM_CELLS * sizeof(Cell))); }
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void free()
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{
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if (buf)
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{
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Allocator::free(buf, getBufferSizeInBytes());
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buf = nullptr;
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}
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}
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void destroyElements()
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{
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if (!std::is_trivially_destructible_v<Cell>)
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for (iterator it = begin(), it_end = end(); it != it_end; ++it)
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it.ptr->~Cell();
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}
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template <typename Derived, bool is_const>
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class iterator_base
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{
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using Container = std::conditional_t<is_const, const Self, Self>;
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using cell_type = std::conditional_t<is_const, const Cell, Cell>;
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Container * container;
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cell_type * ptr;
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friend class FixedHashTable;
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public:
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iterator_base() {}
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iterator_base(Container * container_, cell_type * ptr_) : container(container_), ptr(ptr_)
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{
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cell.update(ptr - container->buf, ptr);
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}
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bool operator==(const iterator_base & rhs) const { return ptr == rhs.ptr; }
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bool operator!=(const iterator_base & rhs) const { return ptr != rhs.ptr; }
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Derived & operator++()
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{
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++ptr;
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/// Skip empty cells in the main buffer.
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auto buf_end = container->buf + container->NUM_CELLS;
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while (ptr < buf_end && ptr->isZero(*container))
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++ptr;
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return static_cast<Derived &>(*this);
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}
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auto & operator*()
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{
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if (cell.key != ptr - container->buf)
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cell.update(ptr - container->buf, ptr);
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return cell;
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}
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auto * operator-> ()
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{
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if (cell.key != ptr - container->buf)
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cell.update(ptr - container->buf, ptr);
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return &cell;
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}
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auto getPtr() const { return ptr; }
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size_t getHash() const { return ptr - container->buf; }
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size_t getCollisionChainLength() const { return 0; }
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typename cell_type::CellExt cell;
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};
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public:
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using key_type = Key;
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using mapped_type = typename Cell::mapped_type;
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using value_type = typename Cell::value_type;
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using cell_type = Cell;
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using LookupResult = Cell *;
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using ConstLookupResult = const Cell *;
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size_t hash(const Key & x) const { return x; }
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FixedHashTable() { alloc(); }
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FixedHashTable(FixedHashTable && rhs) : buf(nullptr) { *this = std::move(rhs); }
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~FixedHashTable()
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{
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destroyElements();
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free();
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}
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FixedHashTable & operator=(FixedHashTable && rhs)
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{
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destroyElements();
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free();
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std::swap(buf, rhs.buf);
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std::swap(m_size, rhs.m_size);
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Allocator::operator=(std::move(rhs));
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Cell::State::operator=(std::move(rhs));
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return *this;
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}
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class Reader final : private Cell::State
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{
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public:
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Reader(DB::ReadBuffer & in_) : in(in_) {}
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Reader(const Reader &) = delete;
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Reader & operator=(const Reader &) = delete;
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bool next()
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{
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if (!is_initialized)
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{
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Cell::State::read(in);
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DB::readVarUInt(size, in);
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is_initialized = true;
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}
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if (read_count == size)
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{
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is_eof = true;
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return false;
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}
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cell.read(in);
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++read_count;
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return true;
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}
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inline const value_type & get() const
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{
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if (!is_initialized || is_eof)
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throw DB::Exception("No available data", DB::ErrorCodes::NO_AVAILABLE_DATA);
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return cell.getValue();
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}
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private:
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DB::ReadBuffer & in;
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Cell cell;
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size_t read_count = 0;
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size_t size;
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bool is_eof = false;
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bool is_initialized = false;
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};
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class iterator : public iterator_base<iterator, false>
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{
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public:
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using iterator_base<iterator, false>::iterator_base;
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};
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class const_iterator : public iterator_base<const_iterator, true>
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{
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public:
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using iterator_base<const_iterator, true>::iterator_base;
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};
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const_iterator begin() const
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{
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if (!buf)
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return end();
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const Cell * ptr = buf;
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auto buf_end = buf + NUM_CELLS;
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while (ptr < buf_end && ptr->isZero(*this))
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++ptr;
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return const_iterator(this, ptr);
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}
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const_iterator cbegin() const { return begin(); }
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iterator begin()
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{
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if (!buf)
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return end();
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Cell * ptr = buf;
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auto buf_end = buf + NUM_CELLS;
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while (ptr < buf_end && ptr->isZero(*this))
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++ptr;
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return iterator(this, ptr);
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}
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const_iterator end() const { return const_iterator(this, buf + NUM_CELLS); }
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const_iterator cend() const { return end(); }
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iterator end() { return iterator(this, buf + NUM_CELLS); }
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public:
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/// The last parameter is unused but exists for compatibility with HashTable interface.
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void ALWAYS_INLINE emplace(const Key & x, LookupResult & it, bool & inserted, size_t /* hash */ = 0)
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{
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it = &buf[x];
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if (!buf[x].isZero(*this))
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{
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inserted = false;
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return;
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}
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new (&buf[x]) Cell(x, *this);
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inserted = true;
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++m_size;
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}
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std::pair<LookupResult, bool> ALWAYS_INLINE insert(const value_type & x)
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{
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std::pair<LookupResult, bool> res;
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emplace(Cell::getKey(x), res.first, res.second);
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if (res.second)
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insertSetMapped(res.first->getMapped(), x);
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return res;
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}
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LookupResult ALWAYS_INLINE find(const Key & x) { return !buf[x].isZero(*this) ? &buf[x] : nullptr; }
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ConstLookupResult ALWAYS_INLINE find(const Key & x) const { return const_cast<std::decay_t<decltype(*this)> *>(this)->find(x); }
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LookupResult ALWAYS_INLINE find(const Key &, size_t hash_value) { return !buf[hash_value].isZero(*this) ? &buf[hash_value] : nullptr; }
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ConstLookupResult ALWAYS_INLINE find(const Key & key, size_t hash_value) const
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{
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return const_cast<std::decay_t<decltype(*this)> *>(this)->find(key, hash_value);
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}
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bool ALWAYS_INLINE has(const Key & x) const { return !buf[x].isZero(*this); }
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bool ALWAYS_INLINE has(const Key &, size_t hash_value) const { return !buf[hash_value].isZero(*this); }
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void write(DB::WriteBuffer & wb) const
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{
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Cell::State::write(wb);
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DB::writeVarUInt(m_size, wb);
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for (auto ptr = buf, buf_end = buf + NUM_CELLS; ptr < buf_end; ++ptr)
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if (!ptr->isZero(*this))
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{
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DB::writeVarUInt(ptr - buf);
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ptr->write(wb);
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}
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}
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void writeText(DB::WriteBuffer & wb) const
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{
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Cell::State::writeText(wb);
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DB::writeText(m_size, wb);
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for (auto ptr = buf, buf_end = buf + NUM_CELLS; ptr < buf_end; ++ptr)
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{
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if (!ptr->isZero(*this))
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{
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DB::writeChar(',', wb);
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DB::writeText(ptr - buf, wb);
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DB::writeChar(',', wb);
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ptr->writeText(wb);
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}
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}
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}
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void read(DB::ReadBuffer & rb)
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{
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Cell::State::read(rb);
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destroyElements();
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DB::readVarUInt(m_size, rb);
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free();
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alloc();
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for (size_t i = 0; i < m_size; ++i)
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{
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size_t place_value = 0;
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DB::readVarUInt(place_value, rb);
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Cell x;
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x.read(rb);
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new (&buf[place_value]) Cell(x, *this);
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}
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}
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void readText(DB::ReadBuffer & rb)
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{
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Cell::State::readText(rb);
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destroyElements();
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DB::readText(m_size, rb);
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free();
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alloc();
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for (size_t i = 0; i < m_size; ++i)
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{
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size_t place_value = 0;
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DB::assertChar(',', rb);
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DB::readText(place_value, rb);
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Cell x;
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DB::assertChar(',', rb);
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x.readText(rb);
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new (&buf[place_value]) Cell(x, *this);
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}
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}
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size_t size() const { return m_size; }
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bool empty() const { return 0 == m_size; }
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void clear()
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{
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destroyElements();
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m_size = 0;
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memset(static_cast<void *>(buf), 0, NUM_CELLS * sizeof(*buf));
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}
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/// After executing this function, the table can only be destroyed,
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/// and also you can use the methods `size`, `empty`, `begin`, `end`.
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void clearAndShrink()
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{
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destroyElements();
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m_size = 0;
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free();
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}
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size_t getBufferSizeInBytes() const { return NUM_CELLS * sizeof(Cell); }
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size_t getBufferSizeInCells() const { return NUM_CELLS; }
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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size_t getCollisions() const { return 0; }
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#endif
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};
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