58 lines
1.3 KiB
C++
58 lines
1.3 KiB
C++
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#ifndef MEMGRAPH_MVCC_ATOM_HPP
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#define MEMGRAPH_MVCC_ATOM_HPP
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#include "threading/sync/lockable.hpp"
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#include "transaction.hpp"
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#include "version.hpp"
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namespace mvcc
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{
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template <class T>
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class Atom : public Version<T>,
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public Lockable<>
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{
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public:
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Atom(uint64_t id, T* first)
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: Version<T>(first), id(id)
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{
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// it's illegal that the first version is nullptr. there should be at
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// least one version of a record
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assert(first != nullptr);
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}
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T* first()
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{
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return this->newer();
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}
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// inspects the record change history and returns the record version visible
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// to the current transaction if it exists, otherwise it returns nullptr
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T* latest_visible(const Transaction& t)
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{
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return first()->latest_visible(t);
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}
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// inspects the record change history and returns the newest available
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// version from all transactions
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T& newest_available()
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{
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T* record = this->newer(), newer = this->newer();
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while(newer != nullptr)
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record = newer, newer = record->newer();
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return record;
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}
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// every record has a unique id. 2^64 = 1.8 x 10^19. that should be enough
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// for a looong time :) but keep in mind that some vacuuming would be nice
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// to reuse indices for deleted nodes.
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uint64_t id;
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};
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}
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#endif
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