some small changes for MULTI-TABLE updates and other little fixes

sql/sql_class.h:
  small optimisations for MULTI-TABLE UPDATE's
sql/sql_parse.cc:
  Could not look at that if () at the start of execute_command, and as 
  Monty evidently did not have time, so I optimised it away in the best 
  fashion I know of.
sql/sql_update.cc:
  Some optimisations  for MULTI-TABLE UPDATE's

sql/sql_class.h

@@ -684,7 +684,7 @@ public:
    enum enum_duplicates dupl;
    uint num_of_tables, num_fields, num_updated, *save_time_stamps, *field_sequence;
    int error;
-   bool do_update;
+   bool do_update, not_trans_safe;
  public:
    multi_update(THD *thd_arg, TABLE_LIST *ut, List<Item> &fs, 		 
 		enum enum_duplicates handle_duplicates,  

sql/sql_parse.cc

@@ -1224,8 +1224,6 @@ mysql_execute_command(void)
       (table_rules_on && tables && thd->slave_thread &&
        !tables_ok(thd,tables)))
     DBUG_VOID_RETURN;
-  if (lex->sql_command==SQLCOM_UPDATE &&  select_lex->table_list.elements > 1)
-    lex->sql_command=SQLCOM_MULTI_UPDATE; 
 
   thread_safe_increment(com_stat[lex->sql_command],&LOCK_thread_count);
   switch (lex->sql_command) {
@@ -1697,19 +1695,68 @@ mysql_execute_command(void)
       send_error(&thd->net,ER_WRONG_VALUE_COUNT);
       DBUG_VOID_RETURN;
     }
-    res = mysql_update(thd,tables,
+    if (select_lex->table_list.elements == 1)
-		       select_lex->item_list,
+    {
-		       lex->value_list,
+      res = mysql_update(thd,tables,
-		       select_lex->where,
+			 select_lex->item_list,
-                       (ORDER *) select_lex->order_list.first,
+			 lex->value_list,
-		       select_lex->select_limit,
+			 select_lex->where,
-		       lex->duplicates,
+			 (ORDER *) select_lex->order_list.first,
-		       lex->lock_option);
+			 select_lex->select_limit,
+			 lex->duplicates,
+			 lex->lock_option);
 
 #ifdef DELETE_ITEMS
-    delete select_lex->where;
+      delete select_lex->where;
 #endif
-    break;
+    }
+    else 
+    {
+      multi_update  *result;
+      uint table_count;
+      TABLE_LIST *auxi;
+      lex->sql_command=SQLCOM_MULTI_UPDATE;
+      for (auxi=(TABLE_LIST*) tables, table_count=0 ; auxi ; auxi=auxi->next)
+      {
+	table_count++;
+	auxi->lock_type=TL_WRITE;
+      }
+      if (select_lex->order_list.elements || (select_lex->select_limit && select_lex->select_limit < INT_MAX))
+      {
+	send_error(&thd->net,ER_NOT_ALLOWED_COMMAND); /// will have to come up with something better eventually
+	  DBUG_VOID_RETURN;
+      }
+      tables->grant.want_privilege=(SELECT_ACL & ~tables->grant.privilege);
+      if ((res=open_and_lock_tables(thd,tables)))
+	break;
+      if (!setup_fields(thd,tables,select_lex->item_list,1,0,0) && 
+	  !setup_fields(thd,tables,lex->value_list,0,0,0) &&  ! thd->fatal_error &&
+	  (result=new multi_update(thd,tables,select_lex->item_list,lex->duplicates,
+				   lex->lock_option, table_count)))
+      {
+	List <Item> total_list;
+	List_iterator <Item> field_list(select_lex->item_list);
+	List_iterator <Item> value_list(lex->value_list);
+	Item *item;
+	while ((item=field_list++))
+	  total_list.push_back(item);
+	while ((item=value_list++))
+	  total_list.push_back(item);
+	
+	res=mysql_select(thd,tables,total_list,
+			 select_lex->where,
+			 (ORDER *)NULL,(ORDER *)NULL,(Item *)NULL,
+			 (ORDER *)NULL,
+			 select_lex->options | thd->options |
+			 SELECT_NO_JOIN_CACHE,
+			 result);
+	delete result;
+      }
+      else
+	res= -1;					// Error is not sent
+      close_thread_tables(thd);
+    }
+    break; 
   case SQLCOM_INSERT:
     if (check_access(thd,INSERT_ACL,tables->db,&tables->grant.privilege))
       goto error; /* purecov: inspected */
@@ -1879,59 +1926,6 @@ mysql_execute_command(void)
     close_thread_tables(thd);
     break;
   }
-  case SQLCOM_MULTI_UPDATE:
-    multi_update  *result;
-    uint table_count;
-    TABLE_LIST *auxi;
-    if (check_access(thd,UPDATE_ACL,tables->db,&tables->grant.privilege))
-      goto error;
-    if (grant_option && check_grant(thd,UPDATE_ACL,tables))
-      goto error;
-    if (select_lex->item_list.elements != lex->value_list.elements)
-    {
-      send_error(&thd->net,ER_WRONG_VALUE_COUNT);
-      DBUG_VOID_RETURN;
-    }
-    for (auxi=(TABLE_LIST*) tables, table_count=0 ; auxi ; auxi=auxi->next)
-    {
-      table_count++;
-      auxi->lock_type=TL_WRITE;
-    }
-    if (select_lex->order_list.elements || (select_lex->select_limit && select_lex->select_limit < INT_MAX))
-    {
-      send_error(&thd->net,ER_NOT_ALLOWED_COMMAND); /// will have to come up with something better eventually
-      DBUG_VOID_RETURN;
-    }
-    tables->grant.want_privilege=(SELECT_ACL & ~tables->grant.privilege);
-    if ((res=open_and_lock_tables(thd,tables)))
-      break;
-    if (!setup_fields(thd,tables,select_lex->item_list,1,0,0) && 
-	!setup_fields(thd,tables,lex->value_list,0,0,0) &&  ! thd->fatal_error &&
-	(result=new multi_update(thd,tables,select_lex->item_list,lex->duplicates,
-				 lex->lock_option, table_count)))
-    {
-      List <Item> total_list;
-      List_iterator <Item> field_list(select_lex->item_list);
-      List_iterator <Item> value_list(lex->value_list);
-      Item *item;
-      while ((item=field_list++))
-	total_list.push_back(item);
-      while ((item=value_list++))
-	total_list.push_back(item);
-
-      res=mysql_select(thd,tables,total_list,
-		       select_lex->where,
-		       (ORDER *)NULL,(ORDER *)NULL,(Item *)NULL,
-		       (ORDER *)NULL,
-		       select_lex->options | thd->options |
-		       SELECT_NO_JOIN_CACHE,
-		       result);
-      delete result;
-    }
-    else
-      res= -1;					// Error is not sent
-    close_thread_tables(thd);
-    break;
   case SQLCOM_DROP_TABLE:
   {
     if (check_table_access(thd,DROP_ACL,tables))

sql/sql_update.cc

@@ -359,6 +359,7 @@ multi_update::multi_update(THD *thd_arg, TABLE_LIST *ut, List<Item> &fs,
   tmp_tables = (TABLE **)NULL;
   int counter=0;
   ulong timestamp_query_id;
+  not_trans_safe=false;
   for (TABLE_LIST *dt=ut ; dt ; dt=dt->next,counter++)
   {
     TABLE *table=ut->table;
@@ -420,6 +421,9 @@ multi_update::prepare(List<Item> &values)
       {
 	num_updated++;
 	table_ref->shared=1;
+	if (!not_trans_safe && !table_ref->table->file->has_transactions())
+	  not_trans_safe=true;
+	table_ref->table->no_keyread=1; // to be moved if initialize_tables has to be used
 	break;
       }
     }
@@ -529,6 +533,7 @@ multi_update::~multi_update()
   {
     TABLE *table=table_being_updated->table;
     (void)table->file->extra(HA_EXTRA_READCHECK);
+    table->no_keyread=0;
     if (error) 
       table->time_stamp=save_time_stamps[counter];
   }
@@ -629,27 +634,13 @@ bool multi_update::send_data(List<Item> &values)
   return 0;
 }
 
-
-/* Return true if some table is not transaction safe */
-
-static bool some_table_is_not_transaction_safe (TABLE_LIST *tl)
-{
-  for (; tl ; tl=tl->next)
-  { 
-    if (!(tl->table->file->has_transactions()))
-      return true;
-  }
-  return false;
-}
-
-
 void multi_update::send_error(uint errcode,const char *err)
 {
   /* First send error what ever it is ... */
   ::send_error(&thd->net,errcode,err);
 
   /* reset used flags */
-  update_tables->table->no_keyread=0;
+//  update_tables->table->no_keyread=0;
 
   /* If nothing updated return */
   if (!updated)
@@ -665,8 +656,7 @@ void multi_update::send_error(uint errcode,const char *err)
     In all other cases do attempt updates ...
   */
   if ((table_being_updated->table->file->has_transactions() &&
-       table_being_updated == update_tables) ||
+       table_being_updated == update_tables) || !not_trans_safe)
-      !some_table_is_not_transaction_safe(update_tables->next))
     ha_rollback_stmt(thd);
   else if (do_update)
     VOID(do_updates(true));
@@ -721,7 +711,6 @@ int multi_update::do_updates (bool from_send_error)
     error = tmp_table->file->rnd_init(1);
     if (error) 
       return error;
-    bool not_trans_safe = some_table_is_not_transaction_safe(update_tables);
     while (!(error=tmp_table->file->rnd_next(tmp_table->record[0])) &&
 	   (!thd->killed ||  from_send_error || not_trans_safe))
     {
@@ -756,7 +745,7 @@ bool multi_update::send_eof()
   int error = do_updates(false);   /* do_updates returns 0 if success */
 
   /* reset used flags */
-  update_tables->table->no_keyread=0;
+//  update_tables->table->no_keyread=0;
   if (error == -1) error = 0;
   thd->proc_info="end";
   if (error)
@@ -767,8 +756,7 @@ bool multi_update::send_eof()
    was a non-transaction-safe table involved, since
    modifications in it cannot be rolled back. */
 
-  if (updated &&
+  if (updated || not_trans_safe)
-      (!error || some_table_is_not_transaction_safe(update_tables)))
   {
     mysql_update_log.write(thd,thd->query,thd->query_length);
     Query_log_event qinfo(thd, thd->query);
@@ -777,7 +765,7 @@ bool multi_update::send_eof()
     is not used */
 
     if (mysql_bin_log.is_open() &&  mysql_bin_log.write(&qinfo) &&
-	!some_table_is_not_transaction_safe(update_tables))
+	!not_trans_safe)
       error=1;  /* Log write failed: roll back
 		   the SQL statement */