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vadim4ovadim4o
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1. xact.c: update comments about changing MyProc->xid and MyProc->xmin.
2. varsup.c:ReadNewTransactionId(): don't read nextXid from disk - this func doesn't allocate next xid, so ShmemVariableCache->nextXid may be used (but GetNewTransactionId() must be called first). 3. vacuum.c: change elog(ERROR, "Child item....") to elog(NOTICE) - this is not ERROR, proper handling is just not implemented, yet. 4. s_lock.c: increase S_MAX_BUSY by 2 times. 5. shmem.c:GetSnapshotData(): have to call ReadNewTransactionId() _after_ SpinAcquire(ShmemIndexLock).
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5 files changed

+44
-26
lines changed

5 files changed

+44
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lines changed

‎src/backend/access/transam/varsup.c

Lines changed: 8 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.21 1999/06/03 04:41:40 vadim Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.22 1999/06/06 20:19:33 vadim Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -335,16 +335,13 @@ ReadNewTransactionId(TransactionId *xid)
335335

336336
SpinAcquire(OidGenLockId); /* not good for concurrency... */
337337

338-
if (ShmemVariableCache->xid_count == 0)
339-
{
340-
TransactionId nextid;
341-
342-
VariableRelationGetNextXid(&nextid);
343-
TransactionIdStore(nextid, &(ShmemVariableCache->nextXid));
344-
ShmemVariableCache->xid_count = VAR_XID_PREFETCH;
345-
TransactionIdAdd(&nextid, VAR_XID_PREFETCH);
346-
VariableRelationPutNextXid(nextid);
347-
}
338+
/*
339+
* Note that we don't check is ShmemVariableCache->xid_count equal
340+
* to 0 or not. This will work as long as we don't call
341+
* ReadNewTransactionId() before GetNewTransactionId().
342+
*/
343+
if (ShmemVariableCache->nextXid == 0)
344+
elog(ERROR, "ReadNewTransactionId: ShmemVariableCache->nextXid is not initialized");
348345

349346
TransactionIdStore(ShmemVariableCache->nextXid, xid);
350347

‎src/backend/access/transam/xact.c

Lines changed: 4 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.39 1999/06/03 13:33:12 vadim Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.40 1999/06/06 20:19:34 vadim Exp $
1111
*
1212
* NOTES
1313
* Transaction aborts can now occur two ways:
@@ -942,15 +942,11 @@ CommitTransaction()
942942
/*
943943
* Let others know about no transaction in progress by me.
944944
* Note that this must be done _before_ releasing locks we hold
945-
* and SpinAcquire(ShmemIndexLock) is required - or bad (too high)
946-
* XmaxRecent value might be used by vacuum: UPDATE with xid 0 is
945+
* and SpinAcquire(ShmemIndexLock) is required: UPDATE with xid 0 is
947946
* blocked by xid 1' UPDATE, xid 1 is doing commit while xid 2
948947
* gets snapshot - if xid 2' GetSnapshotData sees xid 1 as running
949-
* then it must see xid 0 as running as well or XmaxRecent = 1
950-
* might be used by concurrent vacuum causing
951-
* ERROR: Child itemid marked as unused
952-
* This bug was reported by Hiroshi Inoue and I was able to reproduce
953-
* it with 3 sessions and gdb. - vadim 06/03/99
948+
* then it must see xid 0 as running as well or it will see two
949+
* tuple versions - one deleted by xid 1 and one inserted by xid 0.
954950
*/
955951
if (MyProc != (PROC *) NULL)
956952
{

‎src/backend/commands/vacuum.c

Lines changed: 22 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.106 1999/06/03 13:25:54 vadim Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.107 1999/06/06 20:19:34 vadim Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -1238,11 +1238,28 @@ vc_rpfheap(VRelStats *vacrelstats, Relation onerel,
12381238
Citemid = PageGetItemId(Cpage,
12391239
ItemPointerGetOffsetNumber(&Ctid));
12401240
if (!ItemIdIsUsed(Citemid))
1241-
elog(ERROR, "Child itemid marked as unused");
1241+
{
1242+
/*
1243+
* This means that in the middle of chain there was
1244+
* tuple updated by older (than XmaxRecent) xaction
1245+
* and this tuple is already deleted by me. Actually,
1246+
* upper part of chain should be removed and seems
1247+
* that this should be handled in vc_scanheap(), but
1248+
* it's not implemented at the moment and so we
1249+
* just stop shrinking here.
1250+
*/
1251+
ReleaseBuffer(Cbuf);
1252+
pfree(vtmove);
1253+
vtmove = NULL;
1254+
elog(NOTICE, "Child itemid in update-chain marked as unused - can't continue vc_rpfheap");
1255+
break;
1256+
}
12421257
tp.t_data = (HeapTupleHeader) PageGetItem(Cpage, Citemid);
12431258
tp.t_self = Ctid;
12441259
tlen = tp.t_len = ItemIdGetLength(Citemid);
12451260
}
1261+
if (vtmove == NULL)
1262+
break;
12461263
/* first, can chain be moved ? */
12471264
for (;;)
12481265
{
@@ -1336,6 +1353,7 @@ vc_rpfheap(VRelStats *vacrelstats, Relation onerel,
13361353
Ptp.t_data = (HeapTupleHeader) PageGetItem(Ppage, Pitemid);
13371354
Assert(Ptp.t_data->t_xmax == tp.t_data->t_xmin);
13381355

1356+
#ifdef NOT_USED /* I'm not sure that this will wotk properly... */
13391357
/*
13401358
* If this tuple is updated version of row and it
13411359
* was created by the same transaction then no one
@@ -1353,6 +1371,7 @@ vc_rpfheap(VRelStats *vacrelstats, Relation onerel,
13531371
WriteBuffer(Pbuf);
13541372
continue;
13551373
}
1374+
#endif
13561375
tp.t_data = Ptp.t_data;
13571376
tlen = tp.t_len = ItemIdGetLength(Pitemid);
13581377
if (freeCbuf)
@@ -1763,7 +1782,7 @@ Elapsed %u/%u sec.",
17631782
page = BufferGetPage(buf);
17641783
num_tuples = 0;
17651784
for (offnum = FirstOffsetNumber;
1766-
offnum < maxoff;
1785+
offnum <= maxoff;
17671786
offnum = OffsetNumberNext(offnum))
17681787
{
17691788
itemid = PageGetItemId(page, offnum);

‎src/backend/storage/buffer/s_lock.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/s_lock.c,v 1.20 1999/05/25 22:04:32 momjian Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/s_lock.c,v 1.21 1999/06/06 20:19:35 vadim Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -28,7 +28,7 @@
2828
* note: total time to cycle through all 16 entries might be about .07 sec.
2929
*/
3030
#define S_NSPINCYCLE 20
31-
#define S_MAX_BUSY 500 * S_NSPINCYCLE
31+
#define S_MAX_BUSY 1000 * S_NSPINCYCLE
3232

3333
int s_spincycle[S_NSPINCYCLE] =
3434
{0, 0, 0, 0, 10000, 0, 0, 0, 10000, 0,

‎src/backend/storage/ipc/shmem.c

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.41 1999/06/03 13:33:13 vadim Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.42 1999/06/06 20:19:35 vadim Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -652,9 +652,15 @@ GetSnapshotData(bool serializable)
652652

653653
snapshot->xip = (TransactionId *) malloc(have * sizeof(TransactionId));
654654
snapshot->xmin = cid;
655-
ReadNewTransactionId(&(snapshot->xmax));
656655

657656
SpinAcquire(ShmemIndexLock);
657+
/*
658+
* Unfortunately, we have to call ReadNewTransactionId()
659+
* after acquiring ShmemIndexLock above. It's not good because of
660+
* ReadNewTransactionId() does SpinAcquire(OidGenLockId) but
661+
* _necessary_.
662+
*/
663+
ReadNewTransactionId(&(snapshot->xmax));
658664

659665
hash_seq((HTAB *) NULL);
660666
while ((result = (ShmemIndexEnt *) hash_seq(ShmemIndex)) != NULL)

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