Fix bug in wasender's xlogid boundary handling, reported by Erik Rijkers.

LogwrtRqst.Write can be set to non-existent FF log segment, we mustn't
try to send that in XLogSend().

Also fix similar bug in ReadRecord(), which I just introduced in the
ReadRecord() refactoring patch.

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 1.362 2010/01/27 15:27:50 heikki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.363 2010/01/27 16:41:09 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3574,6 +3574,12 @@ ReadRecord(XLogRecPtr *RecPtr, int emode_arg, bool fetching_ckpt)
 			NextLogPage(tmpRecPtr);
 			/* We will account for page header size below */
 		}
+
+		if (tmpRecPtr.xrecoff >= XLogFileSize)
+		{
+			(tmpRecPtr.xlogid)++;
+			tmpRecPtr.xrecoff = 0;
+		}
 	}
 	else
 	{

src/backend/replication/walsender.c

@@ -30,7 +30,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.3 2010/01/21 08:19:57 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.4 2010/01/27 16:41:09 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -610,8 +610,8 @@ XLogSend(StringInfo outMsg)
 		return true;
 
 	/*
-	 * We gather multiple records together by issuing just one read() of
-	 * a suitable size, and send them as one CopyData message. Repeat
+	 * We gather multiple records together by issuing just one XLogRead()
+	 * of a suitable size, and send them as one CopyData message. Repeat
 	 * until we've sent everything we can.
 	 */
 	while (XLByteLT(sentPtr, SendRqstPtr))
@@ -628,11 +628,21 @@ XLogSend(StringInfo outMsg)
 		 * The rounding is not only for performance reasons. Walreceiver
 		 * relies on the fact that we never split a WAL record across two
 		 * messages. Since a long WAL record is split at page boundary into
-		 * continuation records, page boundary is alwayssafe cut-off point.
+		 * continuation records, page boundary is always a safe cut-off point.
 		 * We also assume that SendRqstPtr never points in the middle of a
 		 * WAL record.
 		 */
 		startptr = sentPtr;
+		if (startptr.xrecoff >= XLogFileSize)
+		{
+			/*
+			 * crossing a logid boundary, skip the non-existent last log
+			 * segment in previous logical log file.
+			 */
+			startptr.xlogid += 1;
+			startptr.xrecoff = 0;
+		}
+
 		endptr = startptr;
 		XLByteAdvance(endptr, MAX_SEND_SIZE);
 		/* round down to page boundary. */