slave.h, slave.cc:

  Do not flush the position to master.info file if we have a transaction open

sql/slave.cc

@@ -907,6 +907,12 @@ static int exec_event(THD* thd, NET* net, MASTER_INFO* mi, int event_len)
 					     event_len);
   char llbuff[22];
   
+  mi->event_len = event_len; /* Added by Heikki: InnoDB internally stores the
+				master log position it has processed so far;
+				position to store is really
+				mi->pos + mi->pending + mi->event_len
+				since we must store the pos of the END of the
+				current log event */
   if (ev)
   {
     int type_code = ev->get_type_code();
@@ -1017,7 +1023,16 @@ static int exec_event(THD* thd, NET* net, MASTER_INFO* mi, int event_len)
       delete ev;
 
       mi->inc_pos(event_len);
+      
+      if (!(thd->options & (OPTION_NOT_AUTO_COMMIT | OPTION_BEGIN))) {
+
+      	/* We only flush the master info position to the master.info file if
+        the transaction is not open any more: an incomplete transaction will
+      	be rolled back automatically in crash recovery in transactional
+      	table handlers */
+
         flush_master_info(mi);
+      }
       break;
     }
 	  
@@ -1139,10 +1154,16 @@ static int exec_event(THD* thd, NET* net, MASTER_INFO* mi, int event_len)
       }
 
       mi->inc_pos(event_len);
+
+      if (!(thd->options & (OPTION_NOT_AUTO_COMMIT | OPTION_BEGIN)))
         flush_master_info(mi);
+
       break;
     }
 
+    /* Question: in a START or STOP event, what happens if we have transaction
+    open? */
+
     case START_EVENT:
       mi->inc_pos(event_len);
       flush_master_info(mi);
@@ -1168,6 +1189,8 @@ static int exec_event(THD* thd, NET* net, MASTER_INFO* mi, int event_len)
       mi->pos = 4; // skip magic number
       pthread_cond_broadcast(&mi->cond);
       pthread_mutex_unlock(&mi->lock);
+
+      if (!(thd->options & (OPTION_NOT_AUTO_COMMIT | OPTION_BEGIN)))
         flush_master_info(mi);
 #ifndef DBUG_OFF
       if(abort_slave_event_count)

sql/slave.h

@@ -12,6 +12,12 @@ typedef struct st_master_info
 {
   char log_file_name[FN_REFLEN];
   ulonglong pos,pending;
+  int event_len; /* Added by Heikki: InnoDB internally stores the
+                    master log position it has processed so far; the
+                    position to store is really the sum
+		    pos + pending + event_len
+		    here since we must store the pos of the END of the
+                    current log event */
   File fd; // we keep the file open, so we need to remember the file pointer
   IO_CACHE file;
   // the variables below are needed because we can change masters on the fly