116 lines
3.8 KiB
C++
116 lines
3.8 KiB
C++
/*------------------------------------------------------------------------------*
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* Architecture & Implementation of DBMS *
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*------------------------------------------------------------------------------*
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* Copyright 2022 Databases and Information Systems Group TU Dortmund *
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* Visit us at *
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* http://dbis.cs.tu-dortmund.de/cms/en/home/ *
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* *
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL *
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR *
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, *
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR *
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* OTHER DEALINGS IN THE SOFTWARE. *
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* *
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* Authors: *
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* Maximilian Berens <maximilian.berens@tu-dortmund.de> *
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* Roland Kühn <roland.kuehn@cs.tu-dortmund.de> *
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* Jan Mühlig <jan.muehlig@tu-dortmund.de> *
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*------------------------------------------------------------------------------*
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*/
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#pragma once
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#include <cstdint>
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namespace beedb::concurrency
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{
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/**
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* Represents a transaction timestamp, e.g., a begin or end timestamp
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* of a record or begin or commit time of a transaction.
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* The timestamp contains the "real" time (that is a global counter incremented
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* for each new transaction) and a flag that indices the commit-state of the timestamp.
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* The flag may be 1 for committed and else 0.
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*
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* The time "0" in combination with the set committed flag indicates "infinity".
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*/
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class timestamp
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{
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public:
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using timestamp_t = std::uint64_t;
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static auto make_infinity()
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{
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return timestamp{};
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}
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timestamp(const timestamp_t t, bool is_committed) : _timestamp_and_committed_flag((t << 1u) | is_committed)
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{
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}
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timestamp &operator=(const timestamp &) = default;
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~timestamp() = default;
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/**
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* @return True, if the transaction of the timestamp was committed.
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*/
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[[nodiscard]] bool is_committed() const
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{
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return _timestamp_and_committed_flag & 1u;
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}
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/**
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* @return The "real" time without "committed" flag.
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*/
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[[nodiscard]] timestamp_t time() const
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{
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return _timestamp_and_committed_flag >> 1u;
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}
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/**
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* @return True, when this timestamp is "never ending".
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*/
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[[nodiscard]] bool is_infinity() const
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{
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return _timestamp_and_committed_flag == 1u;
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}
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bool operator==(const timestamp other) const
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{
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return other._timestamp_and_committed_flag == _timestamp_and_committed_flag;
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}
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bool operator!=(const timestamp other) const
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{
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return other._timestamp_and_committed_flag != _timestamp_and_committed_flag;
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}
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bool operator<(const timestamp other) const
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{
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return time() < other.time();
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}
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bool operator<=(const timestamp other) const
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{
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return time() <= other.time();
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}
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bool operator>(const timestamp other) const
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{
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return time() > other.time();
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}
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bool operator>=(const timestamp other) const
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{
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return time() >= other.time();
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}
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private:
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timestamp() = default;
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// Time and committed flag (last bit).
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timestamp_t _timestamp_and_committed_flag = 1u;
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};
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} // namespace beedb::concurrency
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