1. MyProc->xid assignment is moved to GetNewTransactionId so newer

   transactions will not assume that MyProc transaction was committed
   before snapshot calculations. With old MyProc->xid assignment
   (in xact.c:StartTransaction()) there was ability to see the same
   row twice (I used gdb for this)!...
2. Assignments of InvalidTransactionId to MyProc->xid and MyProc->xmin
   are moved from xact.c:CommitTransaction() to
   xact.c:RecordTransactionCommit() - this invalidation must be done
   before releasing transaction locks or bad (too high) XmaxRecent value
   might be used by vacuum ("ERROR:  Child itemid marked as unused"
   reported by "Hiroshi Inoue" <Inoue@tpf.co.jp>; once again, gdb
   allowed me reproduce this error).

src/backend/access/transam/varsup.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.20 1999/05/25 16:07:48 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.21 1999/06/03 04:41:40 vadim Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,6 +19,7 @@
 #include <access/xact.h>
 #include <access/heapam.h>
 #include <catalog/catname.h>
+#include <storage/proc.h>
 
 static void GetNewObjectIdBlock(Oid *oid_return, int oid_block_size);
 static void VariableRelationGetNextOid(Oid *oid_return);
@@ -308,6 +309,9 @@ GetNewTransactionId(TransactionId *xid)
 	TransactionIdAdd(&(ShmemVariableCache->nextXid), 1);
 	(ShmemVariableCache->xid_count)--;
 
+	if (MyProc != (PROC *) NULL)
+		MyProc->xid = *xid;
+
 	SpinRelease(OidGenLockId);
 }
 

src/backend/access/transam/xact.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.37 1999/05/31 22:53:59 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.38 1999/06/03 04:41:41 vadim Exp $
  *
  * NOTES
  *		Transaction aborts can now occur two ways:
@@ -646,6 +646,18 @@ RecordTransactionCommit()
 	FlushBufferPool(!TransactionFlushEnabled());
 	if (leak)
 		ResetBufferPool();
+
+	/*
+	 * Let others know about no transaction in progress.
+	 * Note that this must be done _before_ releasing locks
+	 * we hold or bad (too high) XmaxRecent value might be
+	 * used by vacuum.
+	 */
+	if (MyProc != (PROC *) NULL)
+	{
+		MyProc->xid = InvalidTransactionId;
+		MyProc->xmin = InvalidTransactionId;
+	}
 }
 
 
@@ -884,13 +896,6 @@ StartTransaction()
 	 */
 	s->state = TRANS_INPROGRESS;
 
-	/*
-	 * Let others to know about current transaction is in progress - vadim
-	 * 11/26/96
-	 */
-	if (MyProc != (PROC *) NULL)
-		MyProc->xid = s->transactionIdData;
-
 }
 
 /* ---------------
@@ -958,15 +963,6 @@ CommitTransaction()
 	 */
 	s->state = TRANS_DEFAULT;
 
-	/*
-	 * Let others to know about no transaction in progress - vadim
-	 * 11/26/96
-	 */
-	if (MyProc != (PROC *) NULL)
-	{
-		MyProc->xid = InvalidTransactionId;
-		MyProc->xmin = InvalidTransactionId;
-	}
 }
 
 /* --------------------------------