48 lines
1.4 KiB
C++
48 lines
1.4 KiB
C++
#ifndef MEMGRAPH_MVCC_TRANSACTION_HPP
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#define MEMGRAPH_MVCC_TRANSACTION_HPP
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#include <cstdlib>
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#include <cstdint>
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#include <vector>
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#include "commit_log.hpp"
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struct Transaction
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{
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Transaction(uint64_t id, std::vector<uint64_t> active)
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: id(id), cid(1), active(std::move(active)) {}
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// index of this transaction
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uint64_t id;
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// index of the current command in the current transaction;
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uint8_t cid;
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// the ids of the currently active transactions used by the mvcc
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// implementation for snapshot transaction isolation.
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// std::vector is much faster than std::set for fewer number of items
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// we don't expect the number of active transactions getting too large.
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std::vector<uint64_t> active;
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// check weather the transaction with the xid looks committed from the
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// database snapshot given to this transaction
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bool committed(uint64_t xid) const
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{
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// transaction xid is newer than id and therefore not visible at all
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if (xid > id)
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return false;
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// transaction xid is not visible if it's currently active. the
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// active transactions are sorted ascending and therefore we can stop
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// looking as soon as we hit the active transaction with id greater
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// than xid
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for(size_t i = 0; i < active.size(); ++i)
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if(xid <= active[i])
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return false;
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return true;
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}
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};
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#endif
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