Cleanup initialization of Hot Standby. Clarify working with reanalysis

of requirements and documentation on LogStandbySnapshot(). Fixes
two minor bugs reported by Tom Lane that would lead to an incorrect
snapshot after transaction wraparound. Also fix two other problems
discovered that would give incorrect snapshots in certain cases.
ProcArrayApplyRecoveryInfo() substantially rewritten. Some minor
refactoring of xact_redo_apply() and ExpireTreeKnownAssignedTransactionIds().

Author: simonat2ndQuadrant

src/backend/access/transam/xact.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.289 2010/02/26 02:00:34 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.290 2010/05/13 11:15:38 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -4378,7 +4378,7 @@ xact_redo_commit(xl_xact_commit *xlrec, TransactionId xid, XLogRecPtr lsn)
 		LWLockRelease(XidGenLock);
 	}
 
-	if (!InHotStandby)
+	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
 		 * Mark the transaction committed in pg_clog.
@@ -4412,12 +4412,12 @@ xact_redo_commit(xl_xact_commit *xlrec, TransactionId xid, XLogRecPtr lsn)
 		/*
 		 * We must mark clog before we update the ProcArray.
 		 */
-		ExpireTreeKnownAssignedTransactionIds(xid, xlrec->nsubxacts, sub_xids);
+		ExpireTreeKnownAssignedTransactionIds(xid, xlrec->nsubxacts, sub_xids, max_xid);
 
 		/*
 		 * Send any cache invalidations attached to the commit. We must
 		 * maintain the same order of invalidation then release locks as
-		 * occurs in	 .
+		 * occurs in CommitTransaction().
 		 */
 		ProcessCommittedInvalidationMessages(inval_msgs, xlrec->nmsgs,
 								  XactCompletionRelcacheInitFileInval(xlrec),
@@ -4499,7 +4499,12 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
 		LWLockRelease(XidGenLock);
 	}
 
-	if (InHotStandby)
+	if (standbyState == STANDBY_DISABLED)
+	{
+		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		TransactionIdAbortTree(xid, xlrec->nsubxacts, sub_xids);
+	}
+	else
 	{
 		/*
 		 * If a transaction completion record arrives that has as-yet
@@ -4511,17 +4516,14 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
 		 * already. Leave it in.
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
-	}
 
-	/* Mark the transaction aborted in pg_clog, no need for async stuff */
-	TransactionIdAbortTree(xid, xlrec->nsubxacts, sub_xids);
+		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		TransactionIdAbortTree(xid, xlrec->nsubxacts, sub_xids);
 
-	if (InHotStandby)
-	{
 		/*
-		 * We must mark clog before we update the ProcArray.
+		 * We must update the ProcArray after we have marked clog.
 		 */
-		ExpireTreeKnownAssignedTransactionIds(xid, xlrec->nsubxacts, sub_xids);
+		ExpireTreeKnownAssignedTransactionIds(xid, xlrec->nsubxacts, sub_xids, max_xid);
 
 		/*
 		 * There are no flat files that need updating, nor invalidation
@@ -4596,7 +4598,7 @@ xact_redo(XLogRecPtr lsn, XLogRecord *record)
 	{
 		xl_xact_assignment *xlrec = (xl_xact_assignment *) XLogRecGetData(record);
 
-		if (InHotStandby)
+		if (standbyState >= STANDBY_INITIALIZED)
 			ProcArrayApplyXidAssignment(xlrec->xtop,
 										xlrec->nsubxacts, xlrec->xsub);
 	}

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.409 2010/05/03 11:17:52 heikki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.410 2010/05/13 11:15:38 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -5995,6 +5995,7 @@ StartupXLOG(void)
 			if (wasShutdown)
 			{
 				RunningTransactionsData running;
+				TransactionId latestCompletedXid;
 
 				/*
 				 * Construct a RunningTransactions snapshot representing a shut
@@ -6006,6 +6007,9 @@ StartupXLOG(void)
 				running.subxid_overflow = false;
 				running.nextXid = checkPoint.nextXid;
 				running.oldestRunningXid = oldestActiveXID;
+				latestCompletedXid = checkPoint.nextXid;
+				TransactionIdRetreat(latestCompletedXid);
+				running.latestCompletedXid = latestCompletedXid;
 				running.xids = xids;
 
 				ProcArrayApplyRecoveryInfo(&running);
@@ -6154,8 +6158,9 @@ StartupXLOG(void)
 				xlogctl->recoveryLastXTime = recoveryLastXTime;
 				SpinLockRelease(&xlogctl->info_lck);
 
-				/* In Hot Standby mode, keep track of XIDs we've seen */
-				if (InHotStandby && TransactionIdIsValid(record->xl_xid))
+				/* If we are attempting to enter Hot Standby mode, process XIDs we see */
+				if (standbyState >= STANDBY_INITIALIZED &&
+					TransactionIdIsValid(record->xl_xid))
 					RecordKnownAssignedTransactionIds(record->xl_xid);
 
 				RmgrTable[record->xl_rmid].rm_redo(EndRecPtr, record);
@@ -7803,6 +7808,7 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
 			TransactionId *xids;
 			int			nxids;
 			TransactionId oldestActiveXID;
+			TransactionId latestCompletedXid;
 			RunningTransactionsData running;
 
 			oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids);
@@ -7817,6 +7823,9 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
 			running.subxid_overflow = false;
 			running.nextXid = checkPoint.nextXid;
 			running.oldestRunningXid = oldestActiveXID;
+			latestCompletedXid = checkPoint.nextXid;
+			TransactionIdRetreat(latestCompletedXid);
+			running.latestCompletedXid = latestCompletedXid;
 			running.xids = xids;
 
 			ProcArrayApplyRecoveryInfo(&running);