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.

1 files changed, 83 insertions, 76 deletions

diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index ac06d91dc48..c3aa0859963 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -11,12 +11,26 @@
  * containing the tuple.  (VACUUM FULL assumes it's sufficient to have
  * 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) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.49 2002/01/16 23:51:56 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.49.2.1 2005/05/07 21:23:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -109,14 +123,16 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
 
 			return false;
 		}
-		else if (!TransactionIdDidCommit(tuple->t_xmin))
+		else if (TransactionIdIsInProgress(tuple->t_xmin))
+			return false;
+		else if (TransactionIdDidCommit(tuple->t_xmin))
+			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
+		else
 		{
-			if (TransactionIdDidAbort(tuple->t_xmin))
-				tuple->t_infomask |= HEAP_XMIN_INVALID; /* aborted */
+			/* it must have aborted or crashed */
+			tuple->t_infomask |= HEAP_XMIN_INVALID;
 			return false;
 		}
-		else
-			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
 	}
 
 	/* by here, the inserting transaction has committed */
@@ -138,10 +154,13 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
 		return false;
 	}
 
+	if (TransactionIdIsInProgress(tuple->t_xmax))
+		return true;
+
 	if (!TransactionIdDidCommit(tuple->t_xmax))
 	{
-		if (TransactionIdDidAbort(tuple->t_xmax))
-			tuple->t_infomask |= HEAP_XMAX_INVALID;		/* aborted */
+		/* it must have aborted or crashed */
+		tuple->t_infomask |= HEAP_XMAX_INVALID;
 		return true;
 	}
 
@@ -254,14 +273,16 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
 			else
 				return false;	/* deleted before scan started */
 		}
-		else if (!TransactionIdDidCommit(tuple->t_xmin))
+		else if (TransactionIdIsInProgress(tuple->t_xmin))
+			return false;
+		else if (TransactionIdDidCommit(tuple->t_xmin))
+			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
+		else
 		{
-			if (TransactionIdDidAbort(tuple->t_xmin))
-				tuple->t_infomask |= HEAP_XMIN_INVALID; /* aborted */
+			/* it must have aborted or crashed */
+			tuple->t_infomask |= HEAP_XMIN_INVALID;
 			return false;
 		}
-		else
-			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
 	}
 
 	/* by here, the inserting transaction has committed */
@@ -286,10 +307,13 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
 			return false;		/* deleted before scan started */
 	}
 
+	if (TransactionIdIsInProgress(tuple->t_xmax))
+		return true;
+
 	if (!TransactionIdDidCommit(tuple->t_xmax))
 	{
-		if (TransactionIdDidAbort(tuple->t_xmax))
-			tuple->t_infomask |= HEAP_XMAX_INVALID;		/* aborted */
+		/* it must have aborted or crashed */
+		tuple->t_infomask |= HEAP_XMAX_INVALID;
 		return true;
 	}
 
@@ -428,14 +452,16 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple)
 				return HeapTupleInvisible;		/* updated before scan
 												 * started */
 		}
-		else if (!TransactionIdDidCommit(tuple->t_xmin))
+		else if (TransactionIdIsInProgress(tuple->t_xmin))
+			return HeapTupleInvisible;
+		else if (TransactionIdDidCommit(tuple->t_xmin))
+			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
+		else
 		{
-			if (TransactionIdDidAbort(tuple->t_xmin))
-				tuple->t_infomask |= HEAP_XMIN_INVALID;	/* aborted */
+			/* it must have aborted or crashed */
+			tuple->t_infomask |= HEAP_XMIN_INVALID;
 			return HeapTupleInvisible;
 		}
-		else
-			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
 	}
 
 	/* by here, the inserting transaction has committed */
@@ -461,15 +487,14 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple)
 			return HeapTupleInvisible;	/* updated before scan started */
 	}
 
+	if (TransactionIdIsInProgress(tuple->t_xmax))
+		return HeapTupleBeingUpdated;
+
 	if (!TransactionIdDidCommit(tuple->t_xmax))
 	{
-		if (TransactionIdDidAbort(tuple->t_xmax))
-		{
-			tuple->t_infomask |= HEAP_XMAX_INVALID;		/* aborted */
-			return HeapTupleMayBeUpdated;
-		}
-		/* running xact */
-		return HeapTupleBeingUpdated;	/* in updation by other */
+		/* it must have aborted or crashed */
+		tuple->t_infomask |= HEAP_XMAX_INVALID;
+		return HeapTupleMayBeUpdated;
 	}
 
 	/* xmax transaction committed */
@@ -553,19 +578,20 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
 
 			return false;
 		}
-		else if (!TransactionIdDidCommit(tuple->t_xmin))
+		else if (TransactionIdIsInProgress(tuple->t_xmin))
 		{
-			if (TransactionIdDidAbort(tuple->t_xmin))
-			{
-				tuple->t_infomask |= HEAP_XMIN_INVALID;
-				return false;
-			}
 			SnapshotDirty->xmin = tuple->t_xmin;
 			/* XXX shouldn't we fall through to look at xmax? */
 			return true;		/* in insertion by other */
 		}
-		else
+		else if (TransactionIdDidCommit(tuple->t_xmin))
 			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 */
@@ -588,16 +614,17 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
 		return false;
 	}
 
-	if (!TransactionIdDidCommit(tuple->t_xmax))
+	if (TransactionIdIsInProgress(tuple->t_xmax))
 	{
-		if (TransactionIdDidAbort(tuple->t_xmax))
-		{
-			tuple->t_infomask |= HEAP_XMAX_INVALID;		/* aborted */
-			return true;
-		}
-		/* running xact */
 		SnapshotDirty->xmax = tuple->t_xmax;
-		return true;			/* in updation by other */
+		return true;
+	}
+
+	if (!TransactionIdDidCommit(tuple->t_xmax))
+	{
+		/* it must have aborted or crashed */
+		tuple->t_infomask |= HEAP_XMAX_INVALID;
+		return true;
 	}
 
 	/* xmax transaction committed */
@@ -693,14 +720,16 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
 			else
 				return false;	/* deleted before scan started */
 		}
-		else if (!TransactionIdDidCommit(tuple->t_xmin))
+		else if (TransactionIdIsInProgress(tuple->t_xmin))
+			return false;
+		else if (TransactionIdDidCommit(tuple->t_xmin))
+			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
+		else
 		{
-			if (TransactionIdDidAbort(tuple->t_xmin))
-				tuple->t_infomask |= HEAP_XMIN_INVALID;
+			/* it must have aborted or crashed */
+			tuple->t_infomask |= HEAP_XMIN_INVALID;
 			return false;
 		}
-		else
-			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
 	}
 
 	/*
@@ -737,10 +766,13 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
 				return false;	/* deleted before scan started */
 		}
 
+		if (TransactionIdIsInProgress(tuple->t_xmax))
+			return true;
+
 		if (!TransactionIdDidCommit(tuple->t_xmax))
 		{
-			if (TransactionIdDidAbort(tuple->t_xmax))
-				tuple->t_infomask |= HEAP_XMAX_INVALID; /* aborted */
+			/* it must have aborted or crashed */
+			tuple->t_infomask |= HEAP_XMAX_INVALID;
 			return true;
 		}
 
@@ -785,13 +817,6 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
 	 *
 	 * If the inserting transaction aborted, then the tuple was never visible
 	 * 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))
 	{
@@ -828,17 +853,9 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
 			return HEAPTUPLE_INSERT_IN_PROGRESS;
 		else if (TransactionIdDidCommit(tuple->t_xmin))
 			tuple->t_infomask |= HEAP_XMIN_COMMITTED;
-		else if (TransactionIdDidAbort(tuple->t_xmin))
-		{
-			tuple->t_infomask |= HEAP_XMIN_INVALID;
-			return HEAPTUPLE_DEAD;
-		}
 		else
 		{
-			/*
-			 * Not in Progress, Not Committed, Not Aborted - so it's from
-			 * crashed process. - vadim 11/26/96
-			 */
+			/* it must be aborted or crashed */
 			tuple->t_infomask |= HEAP_XMIN_INVALID;
 			return HEAPTUPLE_DEAD;
 		}
@@ -879,22 +896,12 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin)
 			return HEAPTUPLE_DELETE_IN_PROGRESS;
 		else if (TransactionIdDidCommit(tuple->t_xmax))
 			tuple->t_infomask |= HEAP_XMAX_COMMITTED;
-		else if (TransactionIdDidAbort(tuple->t_xmax))
-		{
-			tuple->t_infomask |= HEAP_XMAX_INVALID;
-			return HEAPTUPLE_LIVE;
-		}
 		else
 		{
-			/*
-			 * Not in Progress, Not Committed, Not Aborted - so it's from
-			 * crashed process. - vadim 06/02/97
-			 */
+			/* it must be aborted or crashed */
 			tuple->t_infomask |= HEAP_XMAX_INVALID;
 			return HEAPTUPLE_LIVE;
 		}
-		/* Should only get here if we set XMAX_COMMITTED */
-		Assert(tuple->t_infomask & HEAP_XMAX_COMMITTED);
 	}
 
 	/*