Replication: various small fixes specific to the new binlog format of 5.0

(including one which may explain autobuild's failure of yesterday)


client/mysqlbinlog.cc:
  - In mysqlbinlog, we should not reset the Format event when we see Rotate. If a binlog started with a Format event, it is not going to switch later to 4.0 format.
  I had already did the same fix in Rotate_log_event::exec_event() in replication.
  - Fix for a merge bug.
sql/log_event.cc:
  An event with an uninited catalog (read from a 4.x server) is not the same as an event with a NULL catalog
  (5.0 server which did not specify catalog), the difference is that they are not in the same format;
  so I introduce a way to know if the catalog has been inited or not. This fixes a rpl_trunc_binlog failure
  I had.
  When we leave Load_log_event::exec_event(), we must reset thd->catalog to 0, like we already do
  in Query_log_event::exec_event(). This fixes a Valgrind error which popped in rpl_charset (which may
  be what caused autobuild to crash yesterday).
  And a fix for event's parsing (the position was always computed right because start_dup==end is always true
  and will until we add new string members to Query_log_event.
sql/log_event.h:
  catalog_len changed from uint to int to allow -1, which means "not inited"
  (I preferred to do it like this rather than create a new bool var Query_log_event::catalog_inited
  like we have in Query_log_event::sql_mode_inited; that's because catalog will not use the whole range of int,
  so it's allowed to pick -1 as a special value and have only one var.
sql/slave.cc:
  comments

client/mysqlbinlog.cc

@@ -418,18 +418,6 @@ Create_file event for file_id: %u\n",exv->file_id);
       */
       ev= 0;
       break;
-    case ROTATE_EVENT:
-      /* see comments in sql/slave.cc:process_io_rotate() */
-      if (description_event->binlog_version >= 4)
-      {
-        delete description_event;
-        /* start from format 3 (MySQL 4.0) again */
-        description_event= new Format_description_log_event(3);
-        if (!description_event || !description_event->is_valid())
-          die("Invalid Format_description log event; could be out of memory");
-      }
-      ev->print(result_file, short_form, last_event_info);
-      break;
     default:
       ev->print(result_file, short_form, last_event_info);
     }
@@ -1011,11 +999,13 @@ static int dump_local_log_entries(const char* logname)
     if (!ev)
     {
       if (file->error)
+      {
 	fprintf(stderr,
                 "Could not read entry at offset %s:"
                 "Error in log format or read error\n",
                 llstr(old_off,llbuff));
         error= 1;
+      }
       // file->error == 0 means EOF, that's OK, we break in this case
       break;
     }

sql/log_event.cc

@@ -1034,7 +1034,7 @@ int Query_log_event::write_data(IO_CACHE* file)
     int8store(start, sql_mode);
     start+= 8;
   }
-  if (catalog)
+  if (catalog_len >= 0) // i.e. "catalog inited" (false for 4.0 events)
   {
     *(start++)= Q_CATALOG_CODE;
     *(start++)= (uchar) catalog_len;
@@ -1119,7 +1119,7 @@ Query_log_event::Query_log_event(THD* thd_arg, const char* query_arg,
 Query_log_event::Query_log_event(const char* buf, uint event_len,
                                  const Format_description_log_event *description_event)
   :Log_event(buf, description_event), data_buf(0), query(NULL),
-   catalog(NULL), db(NULL), catalog_len(0), status_vars_len(0),
+   db(NULL), catalog_len(-1), status_vars_len(0),
    flags2_inited(0), sql_mode_inited(0)
 {
   ulong data_len;
@@ -1214,9 +1214,10 @@ Query_log_event::Query_log_event(const char* buf, uint event_len,
         not need (and want) to change start_dup (because this would cut the
         previously marked status vars).
       */
+      pos++;
       if (start_dup==end)
-        start_dup= ++pos;
-      pos+= catalog_len+1;
+        start_dup= pos;
+      pos+= catalog_len+1; // counting the end '\0'
       break;
     default:
       /* That's why you must write status vars in growing order of code */
@@ -1236,11 +1237,15 @@ Query_log_event::Query_log_event(const char* buf, uint event_len,
   
   const char* tmp_buf= data_buf;
   /* Now set event's pointers to point to bits of the new string */
-  if (catalog_len)
+  if (catalog_len >= 0) // we have seen a catalog (zero-length or not)
   {
     catalog= tmp_buf;
     tmp_buf+= (uint) (end-start_dup); /* "seek" to db */
   }
+#ifndef DBUG_OFF
+  else
+    catalog= 0; // for DBUG_PRINT 
+#endif
   db= tmp_buf;
   query= tmp_buf + db_len + 1;
   q_len = data_buf + data_len - query;
@@ -1531,7 +1536,7 @@ end:
     TEMPORARY TABLE don't suffer from these assignments to 0 as DROP TEMPORARY
     TABLE uses the db.table syntax).
   */
-  thd->db= 0;	                        // prevent db from being freed
+  thd->db= thd->catalog= 0;	        // prevent db from being freed
   thd->query= 0;			// just to be sure
   thd->query_length= 0;
   VOID(pthread_mutex_unlock(&LOCK_thread_count));

sql/log_event.h

@@ -604,7 +604,7 @@ public:
      concerned) from here.
   */
 
-  uint catalog_len;				/* <= 255 char */
+  int catalog_len;				// <= 255 char; -1 means uninited
 
   /*
     We want to be able to store a variable number of N-bit status vars:

sql/slave.cc

@@ -372,7 +372,7 @@ int init_relay_log_pos(RELAY_LOG_INFO* rli,const char* log,
           (starting from position 4):
           Format_desc (of slave)
           Rotate (of master)
-          Format_desc (of slave)
+          Format_desc (of master)
           So the Format_desc which really describes the rest of the relay log is
           the 3rd event (it can't be further than that, because we rotate the
           relay log when we queue a Rotate event from the master).
@@ -3873,7 +3873,10 @@ static int process_io_rotate(MASTER_INFO *mi, Rotate_log_event *rev)
     mi->rli.relay_log.description_event_for_queue= new
       Format_description_log_event(3);
   }
-
+  /*
+    Rotate the relay log makes binlog format detection easier (at next slave
+    start or mysqlbinlog)
+  */
   rotate_relay_log(mi); /* will take the right mutexes */
   DBUG_RETURN(0);
 }