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94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
#pragma once
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#include <Core/Types.h>
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#include <Core/UUID.h>
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#include <fmt/format.h>
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#include <IO/WriteHelpers.h>
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namespace DB
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{
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class IDataType;
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using DataTypePtr = std::shared_ptr<const IDataType>;
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class MergeTreeTransaction;
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/// FIXME Transactions: Sequential node numbers in ZooKeeper are Int32, but 31 bit is not enough
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using CSN = UInt64;
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using Snapshot = CSN;
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using LocalTID = UInt64;
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using TIDHash = UInt64;
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namespace Tx
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{
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const CSN UnknownCSN = 0;
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const CSN PrehistoricCSN = 1;
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const CSN CommittingCSN = 2; /// TODO do we really need it?
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const CSN MaxReservedCSN = 2;
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const LocalTID PrehistoricLocalTID = 1;
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const LocalTID DummyLocalTID = 1;
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const LocalTID MaxReservedLocalTID = 16;
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}
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struct TransactionID
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{
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CSN start_csn = 0;
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LocalTID local_tid = 0;
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UUID host_id = UUIDHelpers::Nil;
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bool operator == (const TransactionID & rhs) const
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{
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return start_csn == rhs.start_csn && local_tid == rhs.local_tid && host_id == rhs.host_id;
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}
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bool operator != (const TransactionID & rhs) const
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{
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return !(*this == rhs);
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}
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TIDHash getHash() const;
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bool isEmpty() const
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{
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assert((local_tid == 0) == (start_csn == 0 && host_id == UUIDHelpers::Nil));
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return local_tid == 0;
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}
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bool isPrehistoric() const
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{
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assert((local_tid == Tx::PrehistoricLocalTID) == (start_csn == Tx::PrehistoricCSN));
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return local_tid == Tx::PrehistoricLocalTID;
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}
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static void write(const TransactionID & tid, WriteBuffer & buf);
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static TransactionID read(ReadBuffer & buf);
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};
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namespace Tx
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{
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const TransactionID EmptyTID = {0, 0, UUIDHelpers::Nil};
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const TransactionID PrehistoricTID = {PrehistoricCSN, PrehistoricLocalTID, UUIDHelpers::Nil};
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const TransactionID DummyTID = {PrehistoricCSN, DummyLocalTID, UUIDHelpers::Nil};
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/// So far, that changes will never become visible
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const CSN RolledBackCSN = std::numeric_limits<CSN>::max();
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}
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}
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template<>
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struct fmt::formatter<DB::TransactionID>
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{
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template<typename ParseContext>
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constexpr auto parse(ParseContext & context)
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{
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return context.begin();
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}
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template<typename FormatContext>
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auto format(const DB::TransactionID & tid, FormatContext & context)
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{
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return fmt::format_to(context.out(), "({}, {}, {})", tid.start_csn, tid.local_tid, tid.host_id);
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}
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};
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