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Adjust time qual checking code so that we always check TransactionIdIsInProgress

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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.
This commit is contained in:
Tom Lane
2005-05-07 21:23:24 +00:00
parent 07e3879c95
commit 4beb9cd5eb
1 changed files with 81 additions and 56 deletions
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137
src/backend/utils/time/tqual.c
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@@ -11,12 +11,26 @@
* containing the tuple. (VACUUM FULL assumes it's sufficient to have * containing the tuple. (VACUUM FULL assumes it's sufficient to have
* exclusive lock on the containing relation, instead.) * exclusive lock on the containing relation, instead.)
* *
* NOTE: must check TransactionIdIsInProgress (which looks in PGPROC array)
* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
* pg_clog). Otherwise we have a race condition: we might decide that a
* just-committed transaction crashed, because none of the tests succeed.
* xact.c is careful to record commit/abort in pg_clog before it unsets
* MyProc->xid in PGPROC array. That fixes that problem, but it also
* means there is a window where TransactionIdIsInProgress and
* TransactionIdDidCommit will both return true. If we check only
* TransactionIdDidCommit, we could consider a tuple committed when a
* later GetSnapshotData call will still think the originating transaction
* is in progress, which leads to application-level inconsistency. The
* upshot is that we gotta check TransactionIdIsInProgress first in all
* code paths.
*
* *
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.61 2002/10/08 17:17:19 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.61.2.1 2005/05/07 21:23:24 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@@ -112,14 +126,16 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
return false; return false;
} }
else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple))) else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
return false;
else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
else
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMIN_INVALID; /* aborted */ tuple->t_infomask |= HEAP_XMIN_INVALID;
return false; return false;
} }
else
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
} }
/* by here, the inserting transaction has committed */ /* by here, the inserting transaction has committed */
@@ -141,10 +157,13 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
return false; return false;
} }
if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
return true;
if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple))) if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMAX_INVALID; /* aborted */ tuple->t_infomask |= HEAP_XMAX_INVALID;
return true; return true;
} }
@@ -254,14 +273,16 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
else else
return false; /* deleted before scan started */ return false; /* deleted before scan started */
} }
else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple))) else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
return false;
else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
else
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMIN_INVALID; /* aborted */ tuple->t_infomask |= HEAP_XMIN_INVALID;
return false; return false;
} }
else
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
} }
/* by here, the inserting transaction has committed */ /* by here, the inserting transaction has committed */
@@ -286,10 +307,13 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
return false; /* deleted before scan started */ return false; /* deleted before scan started */
} }
if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
return true;
if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple))) if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMAX_INVALID; /* aborted */ tuple->t_infomask |= HEAP_XMAX_INVALID;
return true; return true;
} }
@@ -427,14 +451,16 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple, CommandId curcid)
return HeapTupleInvisible; /* updated before scan return HeapTupleInvisible; /* updated before scan
* started */ * started */
} }
else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple))) else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
return HeapTupleInvisible;
else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
else
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMIN_INVALID; /* aborted */ tuple->t_infomask |= HEAP_XMIN_INVALID;
return HeapTupleInvisible; return HeapTupleInvisible;
} }
else
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
} }
/* by here, the inserting transaction has committed */ /* by here, the inserting transaction has committed */
@@ -460,15 +486,14 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple, CommandId curcid)
return HeapTupleInvisible; /* updated before scan started */ return HeapTupleInvisible; /* updated before scan started */
} }
if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
return HeapTupleBeingUpdated;
if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple))) if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple))) /* it must have aborted or crashed */
{ tuple->t_infomask |= HEAP_XMAX_INVALID;
tuple->t_infomask |= HEAP_XMAX_INVALID; /* aborted */ return HeapTupleMayBeUpdated;
return HeapTupleMayBeUpdated;
}
/* running xact */
return HeapTupleBeingUpdated; /* in updation by other */
} }
/* xmax transaction committed */ /* xmax transaction committed */
@@ -549,19 +574,20 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
return false; return false;
} }
else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple))) else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple)))
{
tuple->t_infomask |= HEAP_XMIN_INVALID;
return false;
}
SnapshotDirty->xmin = HeapTupleHeaderGetXmin(tuple); SnapshotDirty->xmin = HeapTupleHeaderGetXmin(tuple);
/* XXX shouldn't we fall through to look at xmax? */ /* XXX shouldn't we fall through to look at xmax? */
return true; /* in insertion by other */ return true; /* in insertion by other */
} }
else else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
tuple->t_infomask |= HEAP_XMIN_COMMITTED; tuple->t_infomask |= HEAP_XMIN_COMMITTED;
else
{
/* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMIN_INVALID;
return false;
}
} }
/* by here, the inserting transaction has committed */ /* by here, the inserting transaction has committed */
@@ -584,16 +610,17 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
return false; return false;
} }
if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
{
SnapshotDirty->xmax = HeapTupleHeaderGetXmax(tuple);
return true;
}
if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple))) if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple))) /* it must have aborted or crashed */
{ tuple->t_infomask |= HEAP_XMAX_INVALID;
tuple->t_infomask |= HEAP_XMAX_INVALID; /* aborted */ return true;
return true;
}
/* running xact */
SnapshotDirty->xmax = HeapTupleHeaderGetXmax(tuple);
return true; /* in updation by other */
} }
/* xmax transaction committed */ /* xmax transaction committed */
@@ -686,14 +713,16 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
else else
return false; /* deleted before scan started */ return false; /* deleted before scan started */
} }
else if (!TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple))) else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
return false;
else if (TransactionIdDidCommit(HeapTupleHeaderGetXmin(tuple)))
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
else
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmin(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMIN_INVALID; tuple->t_infomask |= HEAP_XMIN_INVALID;
return false; return false;
} }
else
tuple->t_infomask |= HEAP_XMIN_COMMITTED;
} }
/* /*
@@ -733,10 +762,13 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
return false; /* deleted before scan started */ return false; /* deleted before scan started */
} }
if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
return true;
if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple))) if (!TransactionIdDidCommit(HeapTupleHeaderGetXmax(tuple)))
{ {
if (TransactionIdDidAbort(HeapTupleHeaderGetXmax(tuple))) /* it must have aborted or crashed */
tuple->t_infomask |= HEAP_XMAX_INVALID; /* aborted */ tuple->t_infomask |= HEAP_XMAX_INVALID;
return true; return true;
} }
@@ -785,13 +817,6 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
* *
* If the inserting transaction aborted, then the tuple was never visible * If the inserting transaction aborted, then the tuple was never visible
* to any other transaction, so we can delete it immediately. * to any other transaction, so we can delete it immediately.
*
* NOTE: must check TransactionIdIsInProgress (which looks in PROC array)
* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
* pg_clog). Otherwise we have a race condition where we might decide
* that a just-committed transaction crashed, because none of the
* tests succeed. xact.c is careful to record commit/abort in pg_clog
* before it unsets MyProc->xid in PROC array.
*/ */
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED)) if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{ {