Minor cleanups of atomic ddl code

- Rename DDL_IGNORE_LOG_ENTRY_CODE to DDL_LOG_IGNORE_ENTRY_CODE
  This makes it similar to all other ddl_log_entry_code's.
- Added some new comments
- ddl_log_revert() now returns != 0 if revert didn't succeed

sql/ddl_log.cc

@@ -421,7 +421,7 @@ static bool disable_execute_entry(uint entry_pos)
   uchar buff[1];
   DBUG_ENTER("disable_execute_entry");
 
-  buff[0]= DDL_IGNORE_LOG_ENTRY_CODE;
+  buff[0]= DDL_LOG_IGNORE_ENTRY_CODE;
   DBUG_RETURN(mysql_file_pwrite(global_ddl_log.file_id, buff, sizeof(buff),
                                 global_ddl_log.io_size * entry_pos +
                                 DDL_LOG_ENTRY_TYPE_POS,
@@ -858,7 +858,7 @@ static bool ddl_log_increment_phase_no_lock(uint entry_pos)
       if (ddl_log_entry_phases[action] <= phase)
       {
         DBUG_ASSERT(phase == ddl_log_entry_phases[action]);
-        /* Same effect as setting DDL_IGNORE_LOG_ENTRY_CODE */
+        /* Same effect as setting DDL_LOG_IGNORE_ENTRY_CODE */
         phase= DDL_LOG_FINAL_PHASE;
       }
       file_entry_buf[DDL_LOG_PHASE_POS]= phase;
@@ -1306,7 +1306,7 @@ static int ddl_log_execute_action(THD *thd, MEM_ROOT *mem_root,
               ddl_log_entry->from_name.str,
               ddl_log_entry->tmp_name.str));
 
-  if (ddl_log_entry->entry_type == DDL_IGNORE_LOG_ENTRY_CODE ||
+  if (ddl_log_entry->entry_type == DDL_LOG_IGNORE_ENTRY_CODE ||
       ddl_log_entry->phase == DDL_LOG_FINAL_PHASE)
     DBUG_RETURN(FALSE);
 
@@ -1421,7 +1421,7 @@ static int ddl_log_execute_action(THD *thd, MEM_ROOT *mem_root,
       (void) file->ha_rename_table(ddl_log_entry->tmp_name.str,
                                    ddl_log_entry->name.str);
       /* disable the entry and sync */
-      file_entry_buf[DDL_LOG_ENTRY_TYPE_POS]= DDL_IGNORE_LOG_ENTRY_CODE;
+      file_entry_buf[DDL_LOG_ENTRY_TYPE_POS]= DDL_LOG_IGNORE_ENTRY_CODE;
       (void) write_ddl_log_file_entry(entry_pos);
       (void) ddl_log_sync_no_lock();
       break;
@@ -2400,7 +2400,7 @@ static bool ddl_log_execute_entry_no_lock(THD *thd, uint first_entry)
       break;
     }
     DBUG_ASSERT(ddl_log_entry.entry_type == DDL_LOG_ENTRY_CODE ||
-                ddl_log_entry.entry_type == DDL_IGNORE_LOG_ENTRY_CODE);
+                ddl_log_entry.entry_type == DDL_LOG_IGNORE_ENTRY_CODE);
 
     if (ddl_log_execute_action(thd, &mem_root, &ddl_log_entry))
     {
@@ -2902,23 +2902,24 @@ void ddl_log_complete(DDL_LOG_STATE *state)
   This is called for failed rename table, create trigger or drop trigger.
 */
 
-void ddl_log_revert(THD *thd, DDL_LOG_STATE *state)
+bool ddl_log_revert(THD *thd, DDL_LOG_STATE *state)
 {
+  bool res= 0;
   DBUG_ENTER("ddl_log_revert");
 
   if (unlikely(!state->list))
-    DBUG_VOID_RETURN;                           // ddl log not used
+    DBUG_RETURN(0);                             // ddl log not used
 
   mysql_mutex_lock(&LOCK_gdl);
   if (likely(state->execute_entry))
   {
-    ddl_log_execute_entry_no_lock(thd, state->list->entry_pos);
+    res= ddl_log_execute_entry_no_lock(thd, state->list->entry_pos);
     ddl_log_disable_execute_entry(&state->execute_entry);
   }
   ddl_log_release_entries(state);
   mysql_mutex_unlock(&LOCK_gdl);
   state->list= 0;
-  DBUG_VOID_RETURN;
+  DBUG_RETURN(res);
 }
 
 
@@ -3124,6 +3125,16 @@ bool ddl_log_drop_view_init(THD *thd, DDL_LOG_STATE *ddl_state,
                            db, &empty_clex_str);
 }
 
+
+/**
+   Log DROP TABLE to the ddl log.
+
+   This code does not call ddl_log_write() as we want the events to
+   be stored in call order instead of reverse order, which is the normal
+   case for all other events.
+   See also comment before ddl_log_drop_init().
+*/
+
 static bool ddl_log_drop(THD *thd, DDL_LOG_STATE *ddl_state,
                          ddl_log_action_code action_code,
                          uint phase,

sql/ddl_log.h

@@ -34,13 +34,13 @@ enum ddl_log_entry_code
     DDL_LOG_ENTRY_CODE:
       An entry to be executed in a linked list from an execute log
       entry.
-    DDL_IGNORE_LOG_ENTRY_CODE:
+    DDL_LOG_IGNORE_ENTRY_CODE:
       An entry that is to be ignored
   */
   DDL_LOG_UNKNOWN= 0,
   DDL_LOG_EXECUTE_CODE= 1,
   DDL_LOG_ENTRY_CODE= 2,
-  DDL_IGNORE_LOG_ENTRY_CODE= 3,
+  DDL_LOG_IGNORE_ENTRY_CODE= 3,
   DDL_LOG_ENTRY_CODE_LAST= 4
 };
 
@@ -267,7 +267,7 @@ bool ddl_log_write_execute_entry(uint first_entry,
 bool ddl_log_disable_execute_entry(DDL_LOG_MEMORY_ENTRY **active_entry);
 
 void ddl_log_complete(DDL_LOG_STATE *ddl_log_state);
-void ddl_log_revert(THD *thd, DDL_LOG_STATE *ddl_log_state);
+bool ddl_log_revert(THD *thd, DDL_LOG_STATE *ddl_log_state);
 
 bool ddl_log_update_phase(DDL_LOG_STATE *entry, uchar phase);
 bool ddl_log_add_flag(DDL_LOG_STATE *entry, uint16 flag);

sql/sql_trigger.cc

@@ -697,7 +697,7 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   ddl_log_complete(&ddl_log_state);
   debug_crash_here("ddl_log_drop_before_delete_tmp");
   /* delete any created log files */
-  ddl_log_revert(thd, &ddl_log_state_tmp_file);
+  result|= ddl_log_revert(thd, &ddl_log_state_tmp_file);
   /*
     If we are under LOCK TABLES we should restore original state of
     meta-data locks. Otherwise all locks will be released along