beedb/include/execution/aggregate_operator.h

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/*------------------------------------------------------------------------------*
* 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 "unary_operator.h"
#include <cstddef>
#include <execution/aggregator.h>
#include <string_view>
#include <table/memory_table.h>
#include <unordered_map>
#include <utility>
#include <vector>
namespace beedb::execution
{
class GroupByKey
{
public:
GroupByKey(const std::vector<std::pair<std::uint16_t, std::uint16_t>> &grouped_columns,
const std::uint16_t grouped_row_size, const table::Tuple &tuple)
{
_data = new std::byte[grouped_row_size];
auto current_index = 0u;
for (const auto &[column_id, _] : grouped_columns)
{
const auto &column = tuple.schema().column(column_id);
const auto size = column.type().size();
std::memcpy(&_data[current_index], &tuple.data()[tuple.schema().offset(column_id)], size);
current_index += size;
}
}
GroupByKey(const GroupByKey &) = delete;
GroupByKey(GroupByKey &&other) noexcept : _data(other._data)
{
other._data = nullptr;
}
~GroupByKey()
{
delete[] _data;
}
bool operator==(const GroupByKey &other) const
{
return std::strcmp(reinterpret_cast<const char *>(_data), reinterpret_cast<const char *>(other._data)) == 0;
}
explicit operator std::string_view() const
{
return std::string_view{reinterpret_cast<const char *>(this->_data)};
}
private:
std::byte *_data;
};
class AggregateOperator : public UnaryOperator
{
public:
AggregateOperator(concurrency::Transaction *transaction, table::Schema &&schema,
std::vector<std::pair<std::uint16_t, std::uint16_t>> &&groups,
std::unordered_map<expression::Term, std::unique_ptr<AggregatorInterface>> &&aggregators);
~AggregateOperator() override = default;
void open() override;
util::optional<table::Tuple> next() override;
void close() override;
[[nodiscard]] const table::Schema &schema() const override
{
return _schema;
}
private:
// The output schema, generated by this operator.
const table::Schema _schema;
// List of [output tuple schema index, aggregator]. The aggregator will produce
// a value for the tuple at the given index.
std::vector<std::pair<std::uint16_t, std::unique_ptr<AggregatorInterface>>> _aggregators;
// Map of child attribute index to this attribute index.
std::vector<std::pair<std::uint16_t, std::uint16_t>> _group_attribute_map;
// Because next() will be called multiple times, we have to
// remember if we have grouped, yet.
bool _has_grouped = false;
// Because next() will be called multiple times, we have to
// remember if we have aggregated, yet.
bool _has_aggregated = false;
// List of grouped tiles. May be empty, even if we have grouped.
std::vector<table::MemoryTable> _tiles;
// Because next() will be called multiple times, we have to remember
// the index of the tile we want to aggregate.
std::size_t _current_tile = 0u;
/**
* Groups the tuples returned by the given child into "tiles", which are
* memory tables, containing all tuples with the identical group key.
*
* @param group_attribute_map List of indices to group.
* @param source Child that produces tuples.
* @return List of tiles.
*/
static std::vector<table::MemoryTable> group(
const std::vector<std::pair<std::uint16_t, std::uint16_t>> &group_attribute_map,
const std::unique_ptr<OperatorInterface> &source);
};
} // namespace beedb::execution
namespace std
{
template <> struct hash<beedb::execution::GroupByKey>
{
public:
std::size_t operator()(const beedb::execution::GroupByKey &key) const
{
return std::hash<std::string_view>()(static_cast<std::string_view>(key));
}
};
} // namespace std