[Issue #225] ptrack LSN should be compared with parent Start LSN instead of parent Stop LSN

Author: gsmolk

src/backup.c

@@ -237,19 +237,19 @@ do_backup_instance(PGconn *backup_conn, PGNodeInfo *nodeInfo, bool no_sync)
 
 	/*
 	 * It`s illegal to take PTRACK backup if LSN from ptrack_control() is not
-	 * equal to stop_lsn of previous backup.
+	 * equal to start_lsn of previous backup.
 	 */
 	if (current.backup_mode == BACKUP_MODE_DIFF_PTRACK)
 	{
 		XLogRecPtr	ptrack_lsn = get_last_ptrack_lsn(backup_conn, nodeInfo);
 
-		if (ptrack_lsn > prev_backup->stop_lsn || ptrack_lsn == InvalidXLogRecPtr)
+		if (ptrack_lsn > prev_backup->start_lsn || ptrack_lsn == InvalidXLogRecPtr)
 		{
-			elog(ERROR, "LSN from ptrack_control %X/%X differs from STOP LSN of previous backup %X/%X.\n"
+			elog(ERROR, "LSN from ptrack_control %X/%X differs from Start LSN of previous backup %X/%X.\n"
 						"Create new full backup before an incremental one.",
 						(uint32) (ptrack_lsn >> 32), (uint32) (ptrack_lsn),
-						(uint32) (prev_backup->stop_lsn >> 32),
-						(uint32) (prev_backup->stop_lsn));
+						(uint32) (prev_backup->start_lsn >> 32),
+						(uint32) (prev_backup->start_lsn));
 		}
 	}