Bug#14275000

Fixes for BUG11761686 left a flaw that managed to slip away from testing.
Only effective filtering branch was actually tested with a regression test
added to rpl_filter_tables_not_exist.
The reason of the failure is destuction of too early mem-root-allocated memory 
at the end of the deferred User-var's do_apply_event().

Fixed with bypassing free_root() in the deferred execution branch.
Deallocation of created in do_apply_event() items is done by the base code
through THD::cleanup_after_query() -> free_items() that the parent Query
can't miss.



sql/log_event.cc:
  Do not call free_root() in case the deferred User-var event.
  Necessary methods to the User-var class are added, do_apply_event() refined.
sql/log_event.h:
  Necessary methods to avoid destoying mem-root-based memory at
  User-var applying are defined.

sql/log_event.cc

@@ -5640,6 +5640,9 @@ User_var_log_event::
 User_var_log_event(const char* buf,
                    const Format_description_log_event* description_event)
   :Log_event(buf, description_event)
+#ifndef MYSQL_CLIENT
+  , deferred(false)
+#endif
 {
   /* The Post-Header is empty. The Variable Data part begins immediately. */
   buf+= description_event->common_header_len +
@@ -5848,7 +5851,10 @@ int User_var_log_event::do_apply_event(Relay_log_info const *rli)
   CHARSET_INFO *charset;
 
   if (rli->deferred_events_collecting)
+  {
+    set_deferred();
     return rli->deferred_events->add(this);
+  }
 
   if (!(charset= get_charset(charset_number, MYF(MY_WME))))
     return 1;
@@ -5900,7 +5906,8 @@ int User_var_log_event::do_apply_event(Relay_log_info const *rli)
       return 0;
     }
   }
-  Item_func_set_user_var e(user_var_name, it);
+
+  Item_func_set_user_var *e= new Item_func_set_user_var(user_var_name, it);
   /*
     Item_func_set_user_var can't substitute something else on its place =>
     0 can be passed as last argument (reference on item)
@@ -5909,7 +5916,7 @@ int User_var_log_event::do_apply_event(Relay_log_info const *rli)
     crash the server, so if fix fields fails, we just return with an
     error.
   */
-  if (e.fix_fields(thd, 0))
+  if (e->fix_fields(thd, 0))
     return 1;
 
   /*
@@ -5917,8 +5924,9 @@ int User_var_log_event::do_apply_event(Relay_log_info const *rli)
     a single record and with a single column. Thus, like
     a column value, it could always have IMPLICIT derivation.
    */
-  e.update_hash(val, val_len, type, charset, DERIVATION_IMPLICIT, 0);
-  free_root(thd->mem_root,0);
+  e->update_hash(val, val_len, type, charset, DERIVATION_IMPLICIT, 0);
+  if (!is_deferred())
+    free_root(thd->mem_root,0);
 
   return 0;
 }

sql/log_event.h

@@ -2483,11 +2483,13 @@ class User_var_log_event: public Log_event
   uint charset_number;
   bool is_null;
 #ifndef MYSQL_CLIENT
+  bool deferred;
   User_var_log_event(THD* thd_arg, char *name_arg, uint name_len_arg,
                      char *val_arg, ulong val_len_arg, Item_result type_arg,
 		     uint charset_number_arg)
     :Log_event(), name(name_arg), name_len(name_len_arg), val(val_arg),
-    val_len(val_len_arg), type(type_arg), charset_number(charset_number_arg)
+    val_len(val_len_arg), type(type_arg), charset_number(charset_number_arg),
+    deferred(false)
     { is_null= !val; }
   void pack_info(Protocol* protocol);
 #else
@@ -2500,6 +2502,13 @@ class User_var_log_event: public Log_event
   Log_event_type get_type_code() { return USER_VAR_EVENT;}
 #ifndef MYSQL_CLIENT
   bool write(IO_CACHE* file);
+  /* 
+     Getter and setter for deferred User-event. 
+     Returns true if the event is not applied directly 
+     and which case the applier adjusts execution path.
+  */
+  bool is_deferred() { return deferred; }
+  void set_deferred() { deferred= val; }
 #endif
   bool is_valid() const { return 1; }