Repair sometimes-incorrect computation of StartUpID after a crash, per
example from Rao Kumar. This is a very corner corner-case, requiring a minimum of three closely-spaced database crashes and an unlucky positioning of the second recovery's checkpoint record before you'd notice any problem. But the consequences are dire enough that it's a must-fix.
This commit is contained in:
Tom Lane
parent
baba07173c
commit
39e98d9563
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.115 2003/05/10 18:01:31 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.116 2003/05/22 14:39:28 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -2568,7 +2568,18 @@ StartupXLOG(void)
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ShmemVariableCache->nextOid = checkPoint.nextOid;
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ShmemVariableCache->oidCount = 0;
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ThisStartUpID = checkPoint.ThisStartUpID;
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/*
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* If it was a shutdown checkpoint, then any following WAL entries were
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* created under the next StartUpID; if it was a regular checkpoint then
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* any following WAL entries were created under the same StartUpID.
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* We must replay WAL entries using the same StartUpID they were created
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* under, so temporarily adopt that SUI (see also xlog_redo()).
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*/
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if (wasShutdown)
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ThisStartUpID = checkPoint.ThisStartUpID + 1;
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else
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ThisStartUpID = checkPoint.ThisStartUpID;
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RedoRecPtr = XLogCtl->Insert.RedoRecPtr =
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XLogCtl->SavedRedoRecPtr = checkPoint.redo;
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@ -2672,55 +2683,21 @@ StartupXLOG(void)
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ControlFile->logSeg = openLogSeg + 1;
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Insert = &XLogCtl->Insert;
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Insert->PrevRecord = LastRec;
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XLogCtl->xlblocks[0].xlogid = openLogId;
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XLogCtl->xlblocks[0].xrecoff =
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((EndOfLog.xrecoff - 1) / BLCKSZ + 1) * BLCKSZ;
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/*
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* If the next record will go to the new page then initialize for that
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* one.
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* Tricky point here: readBuf contains the *last* block that the
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* LastRec record spans, not the one it starts in. The last block
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* is indeed the one we want to use.
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*/
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if ((BLCKSZ - EndOfLog.xrecoff % BLCKSZ) < SizeOfXLogRecord)
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EndOfLog.xrecoff += (BLCKSZ - EndOfLog.xrecoff % BLCKSZ);
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if (EndOfLog.xrecoff % BLCKSZ == 0)
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{
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XLogRecPtr NewPageEndPtr;
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NewPageEndPtr = EndOfLog;
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if (NewPageEndPtr.xrecoff >= XLogFileSize)
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{
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/* crossing a logid boundary */
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NewPageEndPtr.xlogid += 1;
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NewPageEndPtr.xrecoff = BLCKSZ;
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}
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else
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NewPageEndPtr.xrecoff += BLCKSZ;
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XLogCtl->xlblocks[0] = NewPageEndPtr;
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Insert->currpage->xlp_magic = XLOG_PAGE_MAGIC;
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if (InRecovery)
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Insert->currpage->xlp_sui = ThisStartUpID;
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else
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Insert->currpage->xlp_sui = ThisStartUpID + 1;
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Insert->currpage->xlp_pageaddr.xlogid = NewPageEndPtr.xlogid;
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Insert->currpage->xlp_pageaddr.xrecoff = NewPageEndPtr.xrecoff - BLCKSZ;
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/* rest of buffer was zeroed in XLOGShmemInit */
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Insert->currpos = (char *) Insert->currpage + SizeOfXLogPHD;
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}
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else
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{
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XLogCtl->xlblocks[0].xlogid = openLogId;
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XLogCtl->xlblocks[0].xrecoff =
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((EndOfLog.xrecoff - 1) / BLCKSZ + 1) * BLCKSZ;
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/*
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* Tricky point here: readBuf contains the *last* block that the
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* LastRec record spans, not the one it starts in. The last block
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* is indeed the one we want to use.
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*/
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Assert(readOff == (XLogCtl->xlblocks[0].xrecoff - BLCKSZ) % XLogSegSize);
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memcpy((char *) Insert->currpage, readBuf, BLCKSZ);
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Insert->currpos = (char *) Insert->currpage +
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(EndOfLog.xrecoff + BLCKSZ - XLogCtl->xlblocks[0].xrecoff);
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/* Make sure rest of page is zero */
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memset(Insert->currpos, 0, INSERT_FREESPACE(Insert));
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}
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Assert(readOff == (XLogCtl->xlblocks[0].xrecoff - BLCKSZ) % XLogSegSize);
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memcpy((char *) Insert->currpage, readBuf, BLCKSZ);
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Insert->currpos = (char *) Insert->currpage +
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(EndOfLog.xrecoff + BLCKSZ - XLogCtl->xlblocks[0].xrecoff);
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/* Make sure rest of page is zero */
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MemSet(Insert->currpos, 0, INSERT_FREESPACE(Insert));
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LogwrtResult.Write = LogwrtResult.Flush = EndOfLog;
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@ -2774,9 +2751,22 @@ StartupXLOG(void)
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MyXactMadeXLogEntry = false;
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MyXactMadeTempRelUpdate = false;
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/*
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* At this point, ThisStartUpID is the largest SUI that we could
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* find evidence for in the WAL entries. But check it against
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* pg_control's latest checkpoint, to make sure that we can't
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* accidentally re-use an already-used SUI.
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*/
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if (ThisStartUpID < ControlFile->checkPointCopy.ThisStartUpID)
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ThisStartUpID = ControlFile->checkPointCopy.ThisStartUpID;
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/*
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* Perform a new checkpoint to update our recovery activity to disk.
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*
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* Note that we write a shutdown checkpoint. This is correct since
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* the records following it will use SUI one more than what is shown
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* in the checkpoint's ThisStartUpID.
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*
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* In case we had to use the secondary checkpoint, make sure that
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* it will still be shown as the secondary checkpoint after this
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* CreateCheckPoint operation; we don't want the broken primary
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@ -2790,21 +2780,39 @@ StartupXLOG(void)
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*/
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XLogCloseRelationCache();
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}
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else
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{
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/*
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* If we are not doing recovery, then we saw a checkpoint with nothing
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* after it, and we can safely use StartUpID equal to one more than
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* the checkpoint's SUI. But just for paranoia's sake, check against
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* pg_control too.
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*/
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ThisStartUpID = checkPoint.ThisStartUpID;
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if (ThisStartUpID < ControlFile->checkPointCopy.ThisStartUpID)
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ThisStartUpID = ControlFile->checkPointCopy.ThisStartUpID;
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}
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/*
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* Preallocate additional log files, if wanted.
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*/
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PreallocXlogFiles(EndOfLog);
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/*
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* Advance StartUpID to one more than the highest value used previously.
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*/
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ThisStartUpID++;
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XLogCtl->ThisStartUpID = ThisStartUpID;
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/*
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* Okay, we're officially UP.
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*/
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InRecovery = false;
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ControlFile->state = DB_IN_PRODUCTION;
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ControlFile->time = time(NULL);
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UpdateControlFile();
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ThisStartUpID++;
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XLogCtl->ThisStartUpID = ThisStartUpID;
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/* Start up the commit log, too */
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StartupCLOG();
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@ -3000,7 +3008,7 @@ CreateCheckPoint(bool shutdown, bool force)
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UpdateControlFile();
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}
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memset(&checkPoint, 0, sizeof(checkPoint));
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MemSet(&checkPoint, 0, sizeof(checkPoint));
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checkPoint.ThisStartUpID = ThisStartUpID;
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checkPoint.time = time(NULL);
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@ -3259,6 +3267,8 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
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ShmemVariableCache->nextXid = checkPoint.nextXid;
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ShmemVariableCache->nextOid = checkPoint.nextOid;
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ShmemVariableCache->oidCount = 0;
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/* Any later WAL records should be run with shutdown SUI plus 1 */
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ThisStartUpID = checkPoint.ThisStartUpID + 1;
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}
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else if (info == XLOG_CHECKPOINT_ONLINE)
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{
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@ -3274,6 +3284,8 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
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ShmemVariableCache->nextOid = checkPoint.nextOid;
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ShmemVariableCache->oidCount = 0;
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}
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/* Any later WAL records should be run with the then-active SUI */
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ThisStartUpID = checkPoint.ThisStartUpID;
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}
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}
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