beedb/include/table/memory_table.h

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2022-04-04 20:25:01 +02:00
/*------------------------------------------------------------------------------*
* Architecture & Implementation of DBMS *
*------------------------------------------------------------------------------*
* Copyright 2022 Databases and Information Systems Group TU Dortmund *
* Visit us at *
* http://dbis.cs.tu-dortmund.de/cms/en/home/ *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL *
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR *
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, *
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR *
* OTHER DEALINGS IN THE SOFTWARE. *
* *
* Authors: *
* Maximilian Berens <maximilian.berens@tu-dortmund.de> *
* Roland Kühn <roland.kuehn@cs.tu-dortmund.de> *
* Jan Mühlig <jan.muehlig@tu-dortmund.de> *
*------------------------------------------------------------------------------*
*/
#pragma once
#include "schema.h"
#include "tuple.h"
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
namespace beedb::table
{
/**
* Stores data in memory.
* Some times, the data can not stay in the buffer from the BufferManager
* and has to be copied to "safe" memory that will not be replaced.
*/
class MemoryTable
{
public:
explicit MemoryTable(const Schema &schema)
: _schema(schema), _row_size(schema.row_size() + sizeof(concurrency::Metadata))
{
allocate(512u);
}
MemoryTable(MemoryTable &&other) noexcept
: _schema(std::move(other._schema)), _row_size(other._row_size), _capacity(other._capacity), _data(other._data)
{
other._data = nullptr;
_tuples.reserve(other._tuples.size());
for (auto &&tuple : other._tuples)
{
_tuples.emplace_back(Tuple{_schema, std::move(tuple)});
}
}
MemoryTable(const MemoryTable &) = delete;
~MemoryTable()
{
std::free(_data);
}
/**
* Copy data from disk (or page) to the memory.
*
* @param tuple Tuple to be copied to memory.
* @return Index within the memory table.
*/
std::size_t add(const Tuple &tuple)
{
// Reallocate if needed.
if (_tuples.size() == _capacity)
{
allocate(_capacity << 1);
}
// At this location, we will copy the tuples data.
auto *data = _data + _tuples.size() * _row_size;
std::memcpy(data, tuple.metadata(), sizeof(concurrency::Metadata));
std::memcpy(data + sizeof(concurrency::Metadata), tuple.data(), _schema.row_size());
_tuples.emplace_back(Tuple{_schema,
{storage::Page::MEMORY_TABLE_PAGE_ID, 0u},
reinterpret_cast<concurrency::Metadata *>(data),
data + sizeof(concurrency::Metadata)});
return _tuples.size() - 1;
}
/**
* @return Constant set of all tuples stored in the memory table.
*/
[[nodiscard]] const std::vector<Tuple> &tuples() const
{
return _tuples;
}
/**
* @return Set of all tuples stored in the memory table.
*/
std::vector<Tuple> &tuples()
{
return _tuples;
}
/**
* @return Schema of this table.
*/
[[nodiscard]] const Schema &schema() const
{
return _schema;
}
/**
* @return True, when the table has no tuples stored.
*/
[[nodiscard]] bool empty() const
{
return _tuples.empty();
}
/**
* @return Number of stored tuples.
*/
[[nodiscard]] std::size_t size() const
{
return _tuples.size();
}
/**
* Grants access to a specific tuple.
* @param index Index of the tuple.
* @return Tuple.
*/
[[nodiscard]] const Tuple &at(const std::size_t index) const
{
return _tuples[index];
}
const Tuple &operator[](const std::size_t index) const
{
return _tuples[index];
}
[[nodiscard]] auto begin() const
{
return _tuples.begin();
}
[[nodiscard]] auto end() const
{
return _tuples.end();
}
private:
Schema _schema;
const std::uint32_t _row_size;
std::uint64_t _capacity = 0u;
std::byte *_data = nullptr;
std::vector<Tuple> _tuples;
void allocate(const std::uint64_t capacity)
{
// Resize capacity.
const auto old_capacity = _capacity;
_capacity = capacity;
// Resize "real" data.
auto *old_data = _data;
_data = static_cast<std::byte *>(std::aligned_alloc(64u, capacity * _row_size));
// Copy old data to new location.
if (old_data != nullptr)
{
std::memmove(_data, old_data, old_capacity * _row_size);
std::free(old_data);
}
// Tell tuples their new location.
for (auto i = 0u; i < _tuples.size(); ++i)
{
_tuples[i].metadata(reinterpret_cast<concurrency::Metadata *>(_data + i * _row_size));
_tuples[i].data(_data + i * _row_size + sizeof(concurrency::Metadata));
}
}
};
} // namespace beedb::table