WL#1036 (print the db in slave error messages).

I extended the task to cleaning error messages, making them look nicer,
and making the output of SHOW SLAVE STATUS (column Last_error) be as complete
as what's printed on the .err file;
previously we would have, for a failure of a replicated LOAD DATA INFILE:
- in the .err, 2 lines:
"duplicate entry 2708 for key 1"
"failed loading SQL_LOAD-5-2-2.info"
- and in SHOW SLAVE STATUS, only:
"failed loading SQL_LOAD-5-2-2.info".
Now SHOW SLAVE STATUS will contain the concatenation of the 2 messages.


sql/log_event.cc:
  Print the default database when replication stops because of an error. Previously, we had:
  "error "Duplicate entry 87987 for key 1", query 'insert into t values(87987)'", ie the db
  was not mentioned, making it hard for cases where the same table name is used in
  several databases.
  Lengthened some error messages (for failing replication of LOAD DATA: mention the table
  and the db).
  Changes so that SHOW SLAVE STATUS reports as complete errors as the .err file.
sql/slave.cc:
  Removed a useless declaration (the rewrite_db() function is already declared in slave.h).
  Added missing ')' in error messages.
  Tried to make error messages look nicer (previously we had
  "do START SLAVE;, error_code=1062"
  now we'll have
  "do START SLAVE; . Error_code=1062".
  This form has been discussed, I agree it's no panacea, but it's still more readable
  like this. To be improved in the future :)
sql/slave.h:
  declarations.

sql/log_event.cc

@@ -1753,7 +1753,7 @@ void Unknown_log_event::print(FILE* file, bool short_form, char* last_db)
 #ifndef MYSQL_CLIENT
 int Query_log_event::exec_event(struct st_relay_log_info* rli)
 {
-  int expected_error,actual_error = 0;
+  int expected_error, actual_error= 0;
   init_sql_alloc(&thd->mem_root, 8192,0);
   thd->db = rewrite_db((char*)db);
 
@@ -1801,19 +1801,30 @@ int Query_log_event::exec_event(struct st_relay_log_info* rli)
       else if (!strcmp(thd->query,"COMMIT"))
 	rli->inside_transaction=0;
 
+      /*
+        If we expected a non-zero error code, and we don't get the same error
+        code, and none of them should be ignored.
+      */
       if ((expected_error != (actual_error = thd->net.last_errno)) &&
 	  expected_error &&
 	  !ignored_error_code(actual_error) &&
 	  !ignored_error_code(expected_error))
       {
-	const char* errmsg = "Slave: did not get the expected error\
- running query from master - expected: '%s' (%d), got '%s' (%d)"; 
-	sql_print_error(errmsg, ER_SAFE(expected_error),
+	slave_print_error(rli, 0,
+                          "Query '%s' did not get the same error as the query \
+got on master - got on master: '%s' (%d), got on slave: '%s' (%d) \
+(default database was '%s')",
+                          query,
+                          ER_SAFE(expected_error),
                           expected_error,
                           actual_error ? thd->net.last_error: "no error",
-			actual_error);
-	thd->query_error = 1;
+                          actual_error,
+                          print_slave_db_safe((char*)db));
+	thd->query_error= 1;
       }
+      /*
+        If we get the same error code as expected, or they should be ignored. 
+      */
       else if (expected_error == actual_error ||
 	       ignored_error_code(actual_error))
       {
@@ -1821,37 +1832,38 @@ int Query_log_event::exec_event(struct st_relay_log_info* rli)
 	*rli->last_slave_error = 0;
 	rli->last_slave_errno = 0;
       }
-    }
-    else
+      /*
+        Other cases: mostly we expected no error and get one.
+      */
+      else if (thd->query_error || thd->fatal_error)
       {
-      // master could be inconsistent, abort and tell DBA to check/fix it
-      VOID(pthread_mutex_lock(&LOCK_thread_count));
-      thd->db = thd->query = 0;
-      VOID(pthread_mutex_unlock(&LOCK_thread_count));
-      thd->variables.convert_set = 0;
-      close_thread_tables(thd);
-      free_root(&thd->mem_root,0);
-      return 1;
+        slave_print_error(rli,actual_error, "Error '%s' on query '%s' \
+(default database was '%s')",
+                          actual_error ? thd->net.last_error :
+                          "unexpected success or fatal error", query,
+                          print_slave_db_safe((char*)db)); 
+        thd->query_error= 1;
       }
     } 
-  thd->db= 0;				// prevent db from being freed
+    /* 
+       End of sanity check. If the test was wrong, the query got a really bad
+       error on the master, which could be inconsistent, abort and tell DBA to
+       check/fix it. check_expected_error() already printed the message to
+       stderr and rli, and set thd->query_error to 1.
+    */
+  } /* End of if (db_ok(... */
+
+end:
+
   VOID(pthread_mutex_lock(&LOCK_thread_count));
+  thd->db= 0;	                        // prevent db from being freed
   thd->query= 0;			// just to be sure
   VOID(pthread_mutex_unlock(&LOCK_thread_count));
   // assume no convert for next query unless set explictly
   thd->variables.convert_set = 0;
   close_thread_tables(thd);      
-      
-  if (thd->query_error || thd->fatal_error)
-  {
-    slave_print_error(rli,actual_error, "error '%s' on query '%s'",
-		      actual_error ? thd->net.last_error :
-		      "unexpected success or fatal error", query);
-    free_root(&thd->mem_root,0);
-    return 1;
-  }
   free_root(&thd->mem_root,0);
-  return Log_event::exec_event(rli); 
+  return (thd->query_error ? thd->query_error : Log_event::exec_event(rli)); 
 }
 
 /*
@@ -1972,8 +1984,11 @@ int Load_log_event::exec_event(NET* net, struct st_relay_log_info* rli,
 	   event in the master log
 	*/
 	sql_print_error("Slave: load data infile at position %s in log \
-'%s' produced %d warning(s)", llstr(log_pos,llbuff), RPL_LOG_NAME, 
-			thd->cuted_fields );
+'%s' produced %d warning(s) (loaded table was '%s', database was '%s')",
+                        llstr(log_pos,llbuff), RPL_LOG_NAME, 
+			thd->cuted_fields,
+                        (char*)table_name,
+                        print_slave_db_safe((char*)db));
       if (net)
         net->pkt_nr= thd->net.pkt_nr;
     }
@@ -2005,8 +2020,9 @@ int Load_log_event::exec_event(NET* net, struct st_relay_log_info* rli,
       err=ER(sql_errno);       
     }
     slave_print_error(rli,sql_errno,
-		      "Error '%s' running load data infile",
-		      err);
+		      "Error '%s' running load data infile \
+(loaded table was '%s', database was '%s')",
+		      err, (char*)table_name, print_slave_db_safe((char*)db));
     free_root(&thd->mem_root,0);
     return 1;
   }
@@ -2014,7 +2030,10 @@ int Load_log_event::exec_event(NET* net, struct st_relay_log_info* rli,
 	    
   if (thd->fatal_error)
   {
-    sql_print_error("Fatal error running LOAD DATA INFILE ");
+    slave_print_error(rli,ER_UNKNOWN_ERROR,
+"Fatal error running \
+LOAD DATA INFILE (loaded table was '%s', database was '%s')",
+                    (char*)table_name, print_slave_db_safe((char*)db));
     return 1;
   }
 
@@ -2311,7 +2330,21 @@ int Execute_load_log_event::exec_event(struct st_relay_log_info* rli)
   */
   if (lev->exec_event(0,rli,1)) 
   {
-    slave_print_error(rli,my_errno, "Failed executing load from '%s'", fname);
+    /*
+      We want to indicate the name of the file that could not be loaded
+      (SQL_LOADxxx).
+      But as we are here we are sure the error is in rli->last_slave_error and
+      rli->last_slave_errno (example of error: duplicate entry for key), so we
+      don't want to overwrite it with the filename.
+      What we want instead is add the filename to the current error message.
+    */
+    char *tmp= my_strdup(rli->last_slave_error,MYF(MY_WME));
+    if (!tmp)
+      goto err;
+    slave_print_error(rli,rli->last_slave_errno, /* ok to re-use the error code */
+                      "%s. Failed executing load from '%s'", 
+                      tmp, fname);
+    my_free(tmp,MYF(0));
     thd->options = save_options;
     goto err;
   }

sql/slave.cc

@@ -74,7 +74,6 @@ static int request_table_dump(MYSQL* mysql, const char* db, const char* table);
 static int create_table_from_dump(THD* thd, NET* net, const char* db,
 				  const char* table_name);
 static int check_master_version(MYSQL* mysql, MASTER_INFO* mi);
-char* rewrite_db(char* db);
 
 
 /*
@@ -290,8 +289,6 @@ err:
   if (need_data_lock)
     pthread_mutex_unlock(&rli->data_lock);
 
-  /* Isn't this strange: if !need_data_lock, we broadcast with no lock ?? */
-
   pthread_mutex_unlock(log_lock);
   DBUG_RETURN ((*errmsg) ? 1 : 0);
 }
@@ -362,7 +359,10 @@ int purge_relay_logs(RELAY_LOG_INFO* rli, THD *thd, bool just_reset,
   rli->pending= 0;
 
   if (!rli->inited)
+  {
+    DBUG_PRINT("info", ("rli->inited == 0"));
     DBUG_RETURN(0);
+  }
 
   DBUG_ASSERT(rli->slave_running == 0);
   DBUG_ASSERT(rli->mi->slave_running == 0);
@@ -828,6 +828,21 @@ static bool sql_slave_killed(THD* thd, RELAY_LOG_INFO* rli)
   return rli->abort_slave || abort_loop || thd->killed;
 }
 
+/*
+  Writes an error message to rli->last_slave_error and rli->last_slave_errno
+  (which will be displayed by SHOW SLAVE STATUS), and prints it to stderr.
+
+  SYNOPSIS
+    slave_print_error()
+    rli		
+    err_code    The error code
+    msg         The error message (usually related to the error code, but can
+                contain more information).
+    ...         (this is printf-like format, with % symbols in msg)
+
+  RETURN VALUES
+    void
+ */
 
 void slave_print_error(RELAY_LOG_INFO* rli, int err_code, const char* msg, ...)
 {
@@ -835,9 +850,16 @@ void slave_print_error(RELAY_LOG_INFO* rli, int err_code, const char* msg, ...)
   va_start(args,msg);
   my_vsnprintf(rli->last_slave_error,
 	       sizeof(rli->last_slave_error), msg, args);
+  rli->last_slave_errno = err_code;
+  /* If the error string ends with '.', do not add a ',' it would be ugly */
+  if (rli->last_slave_error[0] && 
+      (rli->last_slave_error[strlen(rli->last_slave_error)-1] == '.'))
+    sql_print_error("Slave: %s Error_code=%d", rli->last_slave_error,
+                    err_code);
+  else
     sql_print_error("Slave: %s, error_code=%d", rli->last_slave_error,
                     err_code);
-  rli->last_slave_errno = err_code;
+
 }
 
 
@@ -865,6 +887,16 @@ char* rewrite_db(char* db)
   return db;
 }
 
+/*
+  From other comments and tests in code, it looks like
+  sometimes Query_log_event and Load_log_event can have db==0
+  (see rewrite_db() above for example)
+  (cases where this happens are unclear; it may be when the master is 3.23).
+*/
+char* print_slave_db_safe(char* db)
+{
+  return (db ? rewrite_db(db) : (char*) "");
+}
 
 /*
   Checks whether a db matches some do_db and ignore_db rules
@@ -1282,7 +1314,7 @@ file '%s')", fname);
 			   &msg))
     {
       sql_print_error("Failed to open the relay log (relay_log_name='FIRST', \
-relay_log_pos=4");
+relay_log_pos=4)");
       goto err;
     }
     rli->master_log_name[0]= 0;
@@ -1346,7 +1378,7 @@ file '%s')", fname);
     {
       char llbuf[22];
       sql_print_error("Failed to open the relay log (relay_log_name='%s', \
-relay_log_pos=%s", rli->relay_log_name, llstr(rli->relay_log_pos, llbuf));
+relay_log_pos=%s)", rli->relay_log_name, llstr(rli->relay_log_pos, llbuf));
       goto err;
     }
   }
@@ -2142,14 +2174,13 @@ int check_expected_error(THD* thd, RELAY_LOG_INFO* rli, int expected_error)
   case ER_NET_ERROR_ON_WRITE:  
   case ER_SERVER_SHUTDOWN:  
   case ER_NEW_ABORTING_CONNECTION:
-    my_snprintf(rli->last_slave_error, sizeof(rli->last_slave_error), 
-		"Slave: query '%s' partially completed on the master \
+    slave_print_error(rli,expected_error, 
+                      "query '%s' partially completed on the master \
 and was aborted. There is a chance that your master is inconsistent at this \
 point. If you are sure that your master is ok, run this query manually on the\
  slave and then restart the slave with SET GLOBAL SQL_SLAVE_SKIP_COUNTER=1;\
- SLAVE START;", thd->query);
-    rli->last_slave_errno = expected_error;
-    sql_print_error("%s",rli->last_slave_error);
+ SLAVE START; .", thd->query);
+    thd->query_error= 1;
     return 1;
   default:
     return 0;

sql/slave.h

@@ -383,9 +383,10 @@ int add_wild_table_rule(DYNAMIC_ARRAY* a, const char* table_spec);
 void init_table_rule_hash(HASH* h, bool* h_inited);
 void init_table_rule_array(DYNAMIC_ARRAY* a, bool* a_inited);
 char* rewrite_db(char* db);
+char* print_slave_db_safe(char* db);
 int check_expected_error(THD* thd, RELAY_LOG_INFO* rli, int error_code);
 void skip_load_data_infile(NET* net);
-void slave_print_error(RELAY_LOG_INFO* rli,int err_code, const char* msg, ...);
+void slave_print_error(RELAY_LOG_INFO* rli, int err_code, const char* msg, ...);
 
 void end_slave(); /* clean up */
 int init_master_info(MASTER_INFO* mi, const char* master_info_fname,