Fix an old bug in multixact and two-phase commit. Prepared transactions can

be part of multixacts, so allocate a slot for each prepared transaction in
the "oldest member" array in multixact.c. On PREPARE TRANSACTION, transfer
the oldest member value from the current backends slot to the prepared xact
slot. Also save and recover the value from the 2pc state file.

The symptom of the bug was that after a transaction prepared, a shared lock
still held by the prepared transaction was sometimes ignored by other
transactions.

Fix back to 8.1, where both 2PC and multixact were introduced.

3 files changed, 16 insertions, 4 deletions

diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h
index 0836e032e01..f7fe920c7ee 100644
--- a/src/include/access/multixact.h
+++ b/src/include/access/multixact.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/multixact.h,v 1.14 2009/01/01 17:23:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/multixact.h,v 1.15 2009/11/23 09:58:36 heikki Exp $
  */
 #ifndef MULTIXACT_H
 #define MULTIXACT_H
@@ -52,6 +52,8 @@ extern void MultiXactIdSetOldestMember(void);
 extern int	GetMultiXactIdMembers(MultiXactId multi, TransactionId **xids);
 
 extern void AtEOXact_MultiXact(void);
+extern void AtPrepare_MultiXact(void);
+extern void PostPrepare_MultiXact(TransactionId xid);
 
 extern Size MultiXactShmemSize(void);
 extern void MultiXactShmemInit(void);
@@ -67,6 +69,13 @@ extern void MultiXactSetNextMXact(MultiXactId nextMulti,
 extern void MultiXactAdvanceNextMXact(MultiXactId minMulti,
 						  MultiXactOffset minMultiOffset);
 
+extern void multixact_twophase_recover(TransactionId xid, uint16 info,
+						   void *recdata, uint32 len);
+extern void multixact_twophase_postcommit(TransactionId xid, uint16 info,
+							  void *recdata, uint32 len);
+extern void multixact_twophase_postabort(TransactionId xid, uint16 info,
+							 void *recdata, uint32 len);
+
 extern void multixact_redo(XLogRecPtr lsn, XLogRecord *record);
 extern void multixact_desc(StringInfo buf, uint8 xl_info, char *rec);
 
diff --git a/src/include/access/twophase.h b/src/include/access/twophase.h
index 0a39bad4ec7..5652145f8ca 100644
--- a/src/include/access/twophase.h
+++ b/src/include/access/twophase.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/twophase.h,v 1.11 2009/01/01 17:23:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/twophase.h,v 1.12 2009/11/23 09:58:36 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,7 @@
 #define TWOPHASE_H
 
 #include "access/xlogdefs.h"
+#include "storage/backendid.h"
 #include "storage/proc.h"
 #include "utils/timestamp.h"
 
@@ -31,6 +32,7 @@ extern Size TwoPhaseShmemSize(void);
 extern void TwoPhaseShmemInit(void);
 
 extern PGPROC *TwoPhaseGetDummyProc(TransactionId xid);
+extern BackendId TwoPhaseGetDummyBackendId(TransactionId xid);
 
 extern GlobalTransaction MarkAsPreparing(TransactionId xid, const char *gid,
 				TimestampTz prepared_at,
diff --git a/src/include/access/twophase_rmgr.h b/src/include/access/twophase_rmgr.h
index 5f516b8666c..37d03495bc9 100644
--- a/src/include/access/twophase_rmgr.h
+++ b/src/include/access/twophase_rmgr.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/twophase_rmgr.h,v 1.8 2009/09/01 02:54:52 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/access/twophase_rmgr.h,v 1.9 2009/11/23 09:58:36 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,7 +26,8 @@ typedef uint8 TwoPhaseRmgrId;
 #define TWOPHASE_RM_INVAL_ID		2
 #define TWOPHASE_RM_NOTIFY_ID		3
 #define TWOPHASE_RM_PGSTAT_ID		4
-#define TWOPHASE_RM_MAX_ID			TWOPHASE_RM_PGSTAT_ID
+#define TWOPHASE_RM_MULTIXACT_ID	5
+#define TWOPHASE_RM_MAX_ID			TWOPHASE_RM_MULTIXACT_ID
 
 extern const TwoPhaseCallback twophase_recover_callbacks[];
 extern const TwoPhaseCallback twophase_postcommit_callbacks[];