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Commit264a6b1

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committed
The rolled-back flag on serializable xacts was pointless and redundant with
the marked-for-death flag. It was only set for a fleeting moment while atransaction was being cleaned up at rollback. All the places that checkedfor the rolled-back flag should also check the marked-for-death flag, asboth flags mean that the transaction will roll back. I also renamed themarked-for-death into "doomed", which is a lot shorter name.
1 parent0a0e2b5 commit264a6b1

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2 files changed

+29
-34
lines changed

2 files changed

+29
-34
lines changed

‎src/backend/storage/lmgr/predicate.c

Lines changed: 24 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -244,9 +244,9 @@
244244

245245
#defineSxactIsOnFinishedList(sxact) (!SHMQueueIsDetached(&((sxact)->finishedLink)))
246246

247-
#defineSxactIsPrepared(sxact) (((sxact)->flags & SXACT_FLAG_PREPARED) != 0)
248247
#defineSxactIsCommitted(sxact) (((sxact)->flags & SXACT_FLAG_COMMITTED) != 0)
249-
#defineSxactIsRolledBack(sxact) (((sxact)->flags & SXACT_FLAG_ROLLED_BACK) != 0)
248+
#defineSxactIsPrepared(sxact) (((sxact)->flags & SXACT_FLAG_PREPARED) != 0)
249+
#defineSxactIsDoomed(sxact) (((sxact)->flags & SXACT_FLAG_DOOMED) != 0)
250250
#defineSxactIsReadOnly(sxact) (((sxact)->flags & SXACT_FLAG_READ_ONLY) != 0)
251251
#defineSxactHasSummaryConflictIn(sxact) (((sxact)->flags & SXACT_FLAG_SUMMARY_CONFLICT_IN) != 0)
252252
#defineSxactHasSummaryConflictOut(sxact) (((sxact)->flags & SXACT_FLAG_SUMMARY_CONFLICT_OUT) != 0)
@@ -259,7 +259,6 @@
259259
#defineSxactIsDeferrableWaiting(sxact) (((sxact)->flags & SXACT_FLAG_DEFERRABLE_WAITING) != 0)
260260
#defineSxactIsROSafe(sxact) (((sxact)->flags & SXACT_FLAG_RO_SAFE) != 0)
261261
#defineSxactIsROUnsafe(sxact) (((sxact)->flags & SXACT_FLAG_RO_UNSAFE) != 0)
262-
#defineSxactIsMarkedForDeath(sxact) (((sxact)->flags & SXACT_FLAG_MARKED_FOR_DEATH) != 0)
263262

264263
/*
265264
* Compute the hash code associated with a PREDICATELOCKTARGETTAG.
@@ -609,8 +608,8 @@ RWConflictExists(const SERIALIZABLEXACT *reader, const SERIALIZABLEXACT *writer)
609608
Assert(reader!=writer);
610609

611610
/* Check the ends of the purported conflict first. */
612-
if (SxactIsRolledBack(reader)
613-
||SxactIsRolledBack(writer)
611+
if (SxactIsDoomed(reader)
612+
||SxactIsDoomed(writer)
614613
||SHMQueueEmpty(&reader->outConflicts)
615614
||SHMQueueEmpty(&writer->inConflicts))
616615
return false;
@@ -3048,7 +3047,7 @@ SetNewSxactGlobalXmin(void)
30483047

30493048
for (sxact=FirstPredXact();sxact!=NULL;sxact=NextPredXact(sxact))
30503049
{
3051-
if (!SxactIsRolledBack(sxact)
3050+
if (!SxactIsDoomed(sxact)
30523051
&& !SxactIsCommitted(sxact)
30533052
&&sxact!=OldCommittedSxact)
30543053
{
@@ -3113,7 +3112,7 @@ ReleasePredicateLocks(const bool isCommit)
31133112
}
31143113

31153114
Assert(!isCommit||SxactIsPrepared(MySerializableXact));
3116-
Assert(!SxactIsRolledBack(MySerializableXact));
3115+
Assert(!isCommit|| !SxactIsDoomed(MySerializableXact));
31173116
Assert(!SxactIsCommitted(MySerializableXact));
31183117

31193118
/* may not be serializable during COMMIT/ROLLBACK PREPARED */
@@ -3153,9 +3152,7 @@ ReleasePredicateLocks(const bool isCommit)
31533152
MySerializableXact->flags |=SXACT_FLAG_READ_ONLY;
31543153
}
31553154
else
3156-
{
3157-
MySerializableXact->flags |=SXACT_FLAG_ROLLED_BACK;
3158-
}
3155+
MySerializableXact->flags |=SXACT_FLAG_DOOMED;
31593156

31603157
if (!topLevelIsDeclaredReadOnly)
31613158
{
@@ -3531,7 +3528,7 @@ ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
35313528
nextConflict;
35323529

35333530
Assert(sxact!=NULL);
3534-
Assert(SxactIsRolledBack(sxact)||SxactIsCommitted(sxact));
3531+
Assert(SxactIsDoomed(sxact)||SxactIsCommitted(sxact));
35353532
Assert(LWLockHeldByMe(SerializableFinishedListLock));
35363533

35373534
/*
@@ -3736,7 +3733,8 @@ CheckForSerializableConflictOut(const bool visible, const Relation relation,
37363733
if (!SerializationNeededForRead(relation,snapshot))
37373734
return;
37383735

3739-
if (SxactIsMarkedForDeath(MySerializableXact))
3736+
/* Check if someone else has already decided that we need to die */
3737+
if (SxactIsDoomed(MySerializableXact))
37403738
{
37413739
ereport(ERROR,
37423740
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
@@ -3850,11 +3848,9 @@ CheckForSerializableConflictOut(const bool visible, const Relation relation,
38503848
}
38513849
sxact=sxid->myXact;
38523850
Assert(TransactionIdEquals(sxact->topXid,xid));
3853-
if (sxact==MySerializableXact
3854-
||SxactIsRolledBack(sxact)
3855-
||SxactIsMarkedForDeath(sxact))
3851+
if (sxact==MySerializableXact||SxactIsDoomed(sxact))
38563852
{
3857-
/*We can't conflict withour owntransactionor one rolled back. */
3853+
/*Can't conflict withourself or atransactionthat will roll back. */
38583854
LWLockRelease(SerializableXactHashLock);
38593855
return;
38603856
}
@@ -3869,7 +3865,7 @@ CheckForSerializableConflictOut(const bool visible, const Relation relation,
38693865
{
38703866
if (!SxactIsPrepared(sxact))
38713867
{
3872-
sxact->flags |=SXACT_FLAG_MARKED_FOR_DEATH;
3868+
sxact->flags |=SXACT_FLAG_DOOMED;
38733869
LWLockRelease(SerializableXactHashLock);
38743870
return;
38753871
}
@@ -3996,7 +3992,7 @@ CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)
39963992
mypredlocktag=predlock->tag;
39973993
}
39983994
}
3999-
elseif (!SxactIsRolledBack(sxact)
3995+
elseif (!SxactIsDoomed(sxact)
40003996
&& (!SxactIsCommitted(sxact)
40013997
||TransactionIdPrecedes(GetTransactionSnapshot()->xmin,
40023998
sxact->finishedBefore))
@@ -4009,7 +4005,7 @@ CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)
40094005
* Re-check after getting exclusive lock because the other
40104006
* transaction may have flagged a conflict.
40114007
*/
4012-
if (!SxactIsRolledBack(sxact)
4008+
if (!SxactIsDoomed(sxact)
40134009
&& (!SxactIsCommitted(sxact)
40144010
||TransactionIdPrecedes(GetTransactionSnapshot()->xmin,
40154011
sxact->finishedBefore))
@@ -4113,7 +4109,8 @@ CheckForSerializableConflictIn(const Relation relation, const HeapTuple tuple,
41134109
if (!SerializationNeededForWrite(relation))
41144110
return;
41154111

4116-
if (SxactIsMarkedForDeath(MySerializableXact))
4112+
/* Check if someone else has already decided that we need to die */
4113+
if (SxactIsDoomed(MySerializableXact))
41174114
ereport(ERROR,
41184115
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
41194116
errmsg("could not serialize access due to read/write dependencies among transactions"),
@@ -4417,7 +4414,7 @@ OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
44174414
{
44184415
SERIALIZABLEXACT*t0=conflict->sxactOut;
44194416

4420-
if (!SxactIsRolledBack(t0)
4417+
if (!SxactIsDoomed(t0)
44214418
&& (!SxactIsCommitted(t0)
44224419
||t0->commitSeqNo >=writer->commitSeqNo)
44234420
&& (!SxactIsReadOnly(t0)
@@ -4464,7 +4461,7 @@ OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
44644461
errdetail("Cancelled on conflict out to pivot %u, during read.",writer->topXid),
44654462
errhint("The transaction might succeed if retried.")));
44664463
}
4467-
writer->flags |=SXACT_FLAG_MARKED_FOR_DEATH;
4464+
writer->flags |=SXACT_FLAG_DOOMED;
44684465
}
44694466
}
44704467

@@ -4496,7 +4493,8 @@ PreCommit_CheckForSerializationFailure(void)
44964493

44974494
LWLockAcquire(SerializableXactHashLock,LW_EXCLUSIVE);
44984495

4499-
if (SxactIsMarkedForDeath(MySerializableXact))
4496+
/* Check if someone else has already decided that we need to die */
4497+
if (SxactIsDoomed(MySerializableXact))
45004498
{
45014499
LWLockRelease(SerializableXactHashLock);
45024500
ereport(ERROR,
@@ -4513,8 +4511,7 @@ PreCommit_CheckForSerializationFailure(void)
45134511
while (nearConflict)
45144512
{
45154513
if (!SxactIsCommitted(nearConflict->sxactOut)
4516-
&& !SxactIsRolledBack(nearConflict->sxactOut)
4517-
&& !SxactIsMarkedForDeath(nearConflict->sxactOut))
4514+
&& !SxactIsDoomed(nearConflict->sxactOut))
45184515
{
45194516
RWConflictfarConflict;
45204517

@@ -4527,10 +4524,9 @@ PreCommit_CheckForSerializationFailure(void)
45274524
if (farConflict->sxactOut==MySerializableXact
45284525
|| (!SxactIsCommitted(farConflict->sxactOut)
45294526
&& !SxactIsReadOnly(farConflict->sxactOut)
4530-
&& !SxactIsRolledBack(farConflict->sxactOut)
4531-
&& !SxactIsMarkedForDeath(farConflict->sxactOut)))
4527+
&& !SxactIsDoomed(farConflict->sxactOut)))
45324528
{
4533-
nearConflict->sxactOut->flags |=SXACT_FLAG_MARKED_FOR_DEATH;
4529+
nearConflict->sxactOut->flags |=SXACT_FLAG_DOOMED;
45344530
break;
45354531
}
45364532
farConflict= (RWConflict)

‎src/include/storage/predicate_internals.h

Lines changed: 5 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -90,22 +90,21 @@ typedef struct SERIALIZABLEXACT
9090
intpid;/* pid of associated process */
9191
}SERIALIZABLEXACT;
9292

93-
#defineSXACT_FLAG_ROLLED_BACK0x00000001
94-
#defineSXACT_FLAG_COMMITTED0x00000002
93+
#defineSXACT_FLAG_COMMITTED0x00000001/* already committed */
94+
#defineSXACT_FLAG_PREPARED0x00000002/* about to commit */
95+
#defineSXACT_FLAG_DOOMED0x00000004/* will roll back */
9596
/*
9697
* The following flag actually means that the flagged transaction has a
9798
* conflict out *to a transaction which committed ahead of it*. It's hard
9899
* to get that into a name of a reasonable length.
99100
*/
100-
#defineSXACT_FLAG_CONFLICT_OUT0x00000004
101-
#defineSXACT_FLAG_READ_ONLY0x00000008
102-
#defineSXACT_FLAG_MARKED_FOR_DEATH0x00000010
101+
#defineSXACT_FLAG_CONFLICT_OUT0x00000008
102+
#defineSXACT_FLAG_READ_ONLY0x00000010
103103
#defineSXACT_FLAG_DEFERRABLE_WAITING0x00000020
104104
#defineSXACT_FLAG_RO_SAFE0x00000040
105105
#defineSXACT_FLAG_RO_UNSAFE0x00000080
106106
#defineSXACT_FLAG_SUMMARY_CONFLICT_IN0x00000100
107107
#defineSXACT_FLAG_SUMMARY_CONFLICT_OUT0x00000200
108-
#defineSXACT_FLAG_PREPARED0x00000400
109108

110109
/*
111110
* The following types are used to provide an ad hoc list for holding

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