bugfix: cmp_item_row::alloc_comparators() allocated on the wrong arena

it used current_thd->alloc() and allocated on the thd's execution arena,
not on table->expr_arena.

Remove THD::arena_for_cached_items that is temporarily set in
update_virtual_fields(), and replaces THD arena in get_datetime_value().
Instead set THD arena to table->expr_arena for the whole  duration
of update_virtual_fields()

4 files changed, 4 insertions, 27 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 46566206094..ebe088e5092 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -921,12 +921,7 @@ get_datetime_value(THD *thd, Item ***item_arg, Item **cache_arg,
     if (!thd)
       thd= current_thd;
 
-    Query_arena backup;
-    Query_arena *save_arena= thd->switch_to_arena_for_cached_items(&backup);
     Item_cache_temporal *cache= new Item_cache_temporal(f_type);
-    if (save_arena)
-      thd->set_query_arena(save_arena);
-
     cache->store_packed(value, item);
     *cache_arg= cache;
     *item_arg= cache_arg;
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 62339b2690a..93af4d3bb4d 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -957,7 +957,6 @@ THD::THD()
 
   m_internal_handler= NULL;
   m_binlog_invoker= FALSE;
-  arena_for_cached_items= 0;
   memset(&invoker_user, 0, sizeof(invoker_user));
   memset(&invoker_host, 0, sizeof(invoker_host));
   prepare_derived_at_open= FALSE;
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 27bc40e3761..5dd7cd18a5d 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -3102,26 +3102,7 @@ public:
     }
   }
 
-private:
-  /* 
-    This reference points to the table arena when the expression
-    for a virtual column is being evaluated
-  */ 
-  Query_arena *arena_for_cached_items;
-
 public:
-  void reset_arena_for_cached_items(Query_arena *new_arena)
-  {
-    arena_for_cached_items= new_arena;
-  }
-  Query_arena *switch_to_arena_for_cached_items(Query_arena *backup)
-  {
-    if (!arena_for_cached_items)
-      return 0;
-    set_n_backup_active_arena(arena_for_cached_items, backup);
-    return backup;
-  }
-
   void clear_wakeup_ready() { wakeup_ready= false; }
   /*
     Sleep waiting for others to wake us up with signal_wakeup_ready().
diff --git a/sql/table.cc b/sql/table.cc
index 1330560b6b6..9d52d5f87a2 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -6575,7 +6575,9 @@ int update_virtual_fields(THD *thd, TABLE *table,
   int error __attribute__ ((unused))= 0;
   DBUG_ASSERT(table && table->vfield);
 
-  thd->reset_arena_for_cached_items(table->expr_arena);
+  Query_arena backup_arena;
+  thd->set_n_backup_active_arena(table->expr_arena, &backup_arena);
+
   /* Iterate over virtual fields in the table */
   for (vfield_ptr= table->vfield; *vfield_ptr; vfield_ptr++)
   {
@@ -6593,7 +6595,7 @@ int update_virtual_fields(THD *thd, TABLE *table,
       DBUG_PRINT("info", ("field '%s' - skipped", vfield->field_name));
     }
   }
-  thd->reset_arena_for_cached_items(0);
+  thd->restore_active_arena(table->expr_arena, &backup_arena);
   DBUG_RETURN(0);
 }