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Adjust time qual checking code so that we always check TransactionIdIsInProgress
before we check commit/abort status. Formerly this was done in some paths but not all, with the result that a transaction might be considered committed for some purposes before it became committed for others. Per example found by Jan Wieck.
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4cd4ed0cc2
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@ -11,12 +11,28 @@
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* "hint" status bits if we see that the inserting or deleting transaction
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* has now committed or aborted.
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*
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* NOTE: must check TransactionIdIsInProgress (which looks in PGPROC array)
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* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
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* pg_clog). Otherwise we have a race condition: we might decide that a
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* just-committed transaction crashed, because none of the tests succeed.
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* xact.c is careful to record commit/abort in pg_clog before it unsets
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* MyProc->xid in PGPROC array. That fixes that problem, but it also
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* means there is a window where TransactionIdIsInProgress and
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* TransactionIdDidCommit will both return true. If we check only
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* TransactionIdDidCommit, we could consider a tuple committed when a
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* later GetSnapshotData call will still think the originating transaction
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* is in progress, which leads to application-level inconsistency. The
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* upshot is that we gotta check TransactionIdIsInProgress first in all
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* code paths, except for a few cases where we are looking at
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* subtransactions of our own main transaction and so there can't be any
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* race condition.
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*
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*
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* Portions Copyright (c) 1996-2005, 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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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.87 2005/04/28 21:47:16 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.88 2005/05/07 21:22:01 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -147,20 +163,20 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer)
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return false;
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}
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else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
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return false;
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}
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else
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else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else
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{
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return false;
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}
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}
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/* by here, the inserting transaction has committed */
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@ -189,13 +205,14 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer)
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return false;
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}
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if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
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return true;
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if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple)))
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{
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return true;
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}
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@ -330,20 +347,20 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer)
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else
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return false; /* deleted before scan started */
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}
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else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
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return false;
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}
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else
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else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else
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{
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return false;
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}
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}
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/* by here, the inserting transaction has committed */
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@ -375,13 +392,14 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer)
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return false; /* deleted before scan started */
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}
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if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
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return true;
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if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple)))
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{
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return true;
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}
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@ -569,20 +587,20 @@ HeapTupleSatisfiesUpdate(HeapTupleHeader tuple, CommandId curcid,
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return HeapTupleInvisible; /* updated before scan
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* started */
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}
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else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
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return HeapTupleInvisible;
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}
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else
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else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else
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{
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return HeapTupleInvisible;
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}
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}
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/* by here, the inserting transaction has committed */
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@ -620,16 +638,15 @@ HeapTupleSatisfiesUpdate(HeapTupleHeader tuple, CommandId curcid,
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return HeapTupleInvisible; /* updated before scan started */
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}
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if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
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return HeapTupleBeingUpdated;
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if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple)))
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{
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return HeapTupleMayBeUpdated;
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}
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/* running xact */
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return HeapTupleBeingUpdated; /* in updation by other */
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return HeapTupleMayBeUpdated;
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}
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/* xmax transaction committed */
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@ -735,23 +752,24 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
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return false;
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}
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else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return false;
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}
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SnapshotDirty->xmin = HeapTupleHeaderGetXmin(tuple);
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/* XXX shouldn't we fall through to look at xmax? */
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return true; /* in insertion by other */
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}
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else
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else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else
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{
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return false;
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}
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}
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/* by here, the inserting transaction has committed */
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@ -781,17 +799,18 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
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return false;
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}
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if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
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{
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SnapshotDirty->xmax = HeapTupleHeaderGetXmax(tuple);
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return true;
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}
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if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple)))
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{
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return true;
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}
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/* running xact */
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SnapshotDirty->xmax = HeapTupleHeaderGetXmax(tuple);
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return true; /* in updation by other */
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return true;
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}
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/* xmax transaction committed */
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@ -907,20 +926,20 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot,
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else
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return false; /* deleted before scan started */
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}
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else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
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return false;
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}
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else
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else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
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{
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tuple->t_infomask |= HEAP_XMIN_COMMITTED;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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else
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{
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMIN_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return false;
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}
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}
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/*
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@ -982,13 +1001,14 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot,
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return false; /* deleted before scan started */
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}
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if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
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return true;
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if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
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{
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if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple)))
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{
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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}
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/* it must have aborted or crashed */
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tuple->t_infomask |= HEAP_XMAX_INVALID;
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SetBufferCommitInfoNeedsSave(buffer);
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return true;
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}
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@ -1057,13 +1077,6 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin,
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*
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* If the inserting transaction aborted, then the tuple was never visible
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* to any other transaction, so we can delete it immediately.
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*
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* NOTE: must check TransactionIdIsInProgress (which looks in PROC array)
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* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
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* pg_clog). Otherwise we have a race condition where we might decide
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* that a just-committed transaction crashed, because none of the
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* tests succeed. xact.c is careful to record commit/abort in pg_clog
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* before it unsets MyProc->xid in PROC array.
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*/
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if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
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{
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