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Commit5ab0ad5

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VACUUM must make sure that a HEAP_MARKED_FOR_UPDATE tuple gets marked
as either HEAP_XMAX_COMMITTED or HEAP_XMAX_INVALID once the updatingtransaction is gone. Otherwise some other transaction may come alongand try to test the commit status of t_xmax later --- which could beafter VACUUM has recycled the CLOG status for that xact. Bug introducedin post-beta4 bug fix.
1 parenteb5e8ba commit5ab0ad5

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‎src/backend/utils/time/tqual.c

Lines changed: 16 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.45 2001/12/19 17:18:39 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.46 2002/01/11 20:07:03 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -742,7 +742,21 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
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if (tuple->t_infomask&HEAP_MARKED_FOR_UPDATE)
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{
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/* "deleting" xact really only marked it for update */
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/*
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* "Deleting" xact really only marked it for update, so the tuple
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* is live in any case. However, we must make sure that either
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* XMAX_COMMITTED or XMAX_INVALID gets set once the xact is gone;
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* otherwise it is unsafe to recycle CLOG status after vacuuming.
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*/
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if (!(tuple->t_infomask&HEAP_XMAX_COMMITTED))
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{
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if (TransactionIdIsInProgress(tuple->t_xmax))
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returnHEAPTUPLE_LIVE;
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if (TransactionIdDidCommit(tuple->t_xmax))
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tuple->t_infomask |=HEAP_XMAX_COMMITTED;
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else/* it's either aborted or crashed */
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tuple->t_infomask |=HEAP_XMAX_INVALID;
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}
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returnHEAPTUPLE_LIVE;
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}
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