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Commit5a1dfde

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Make use FullTransactionId in 2PC filenames
Switch from using TransactionId to FullTransactionId in naming of 2PC files.Transaction state file in the pg_twophase directory now have extra 8 bytes inthe name to address an epoch of a given xid.Author: Maxim Orlov, Aleksander Alekseev, Alexander Korotkov, Teodor SigaevAuthor: Nikita Glukhov, Pavel Borisov, Yura SokolovReviewed-by: Jacob Champion, Heikki Linnakangas, Alexander KorotkovReviewed-by: Japin Li, Pavel Borisov, Tom Lane, Peter Eisentraut, Andres FreundReviewed-by: Andrey Borodin, Dilip Kumar, Aleksander AlekseevDiscussion:https://postgr.es/m/CACG%3DezZe1NQSCnfHOr78AtAZxJZeCvxrts0ygrxYwe%3DpyyjVWA%40mail.gmail.comDiscussion:https://postgr.es/m/CAJ7c6TPDOYBYrnCAeyndkBktO0WG2xSdYduTF0nxq%2BvfkmTF5Q%40mail.gmail.com
1 parent2cdf131 commit5a1dfde

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‎src/backend/access/transam/twophase.c

Lines changed: 45 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -942,8 +942,46 @@ TwoPhaseGetDummyProc(TransactionId xid, bool lock_held)
942942
/* State file support*/
943943
/************************************************************************/
944944

945-
#defineTwoPhaseFilePath(path,xid) \
946-
snprintf(path, MAXPGPATH, TWOPHASE_DIR "/%08X", xid)
945+
/*
946+
* Compute the FullTransactionId for the given TransactionId.
947+
*
948+
* The wrap logic is safe here because the span of active xids cannot exceed one
949+
* epoch at any given time.
950+
*/
951+
staticinlineFullTransactionId
952+
AdjustToFullTransactionId(TransactionIdxid)
953+
{
954+
FullTransactionIdnextFullXid;
955+
TransactionIdnextXid;
956+
uint32epoch;
957+
958+
Assert(TransactionIdIsValid(xid));
959+
960+
LWLockAcquire(XidGenLock,LW_SHARED);
961+
nextFullXid=ShmemVariableCache->nextXid;
962+
LWLockRelease(XidGenLock);
963+
964+
nextXid=XidFromFullTransactionId(nextFullXid);
965+
epoch=EpochFromFullTransactionId(nextFullXid);
966+
if (unlikely(xid>nextXid))
967+
{
968+
/* Wraparound occured, must be from a prev epoch. */
969+
Assert(epoch>0);
970+
epoch--;
971+
}
972+
973+
returnFullTransactionIdFromEpochAndXid(epoch,xid);
974+
}
975+
976+
staticinlineint
977+
TwoPhaseFilePath(char*path,TransactionIdxid)
978+
{
979+
FullTransactionIdfxid=AdjustToFullTransactionId(xid);
980+
981+
returnsnprintf(path,MAXPGPATH,TWOPHASE_DIR"/%08X%08X",
982+
EpochFromFullTransactionId(fxid),
983+
XidFromFullTransactionId(fxid));
984+
}
947985

948986
/*
949987
* 2PC state file format:
@@ -1882,13 +1920,15 @@ restoreTwoPhaseData(void)
18821920
cldir=AllocateDir(TWOPHASE_DIR);
18831921
while ((clde=ReadDir(cldir,TWOPHASE_DIR))!=NULL)
18841922
{
1885-
if (strlen(clde->d_name)==8&&
1886-
strspn(clde->d_name,"0123456789ABCDEF")==8)
1923+
if (strlen(clde->d_name)==16&&
1924+
strspn(clde->d_name,"0123456789ABCDEF")==16)
18871925
{
18881926
TransactionIdxid;
1927+
FullTransactionIdfxid;
18891928
char*buf;
18901929

1891-
xid= (TransactionId)strtoul(clde->d_name,NULL,16);
1930+
fxid=FullTransactionIdFromU64(strtou64(clde->d_name,NULL,16));
1931+
xid=XidFromFullTransactionId(fxid);
18921932

18931933
buf=ProcessTwoPhaseBuffer(xid,InvalidXLogRecPtr,
18941934
true, false, false);

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