MDEV-30889: 3 - Item_in_optimizer leak

Keep Item_in_optimizer cache always (but only once) in statement memory.

sql/item.cc

@@ -10430,7 +10430,8 @@ int Item_cache_str::save_in_field(Field *field, bool no_conversions)
 bool Item_cache_row::allocate(THD *thd, uint num)
 {
   item_count= num;
-  return (!(values= 
+  return (!values &&
+          !(values=
 	    (Item_cache **) thd->calloc(sizeof(Item_cache *)*item_count)));
 }
 
@@ -10467,10 +10468,11 @@ bool Item_cache_row::setup(THD *thd, Item *item)
   for (uint i= 0; i < item_count; i++)
   {
     Item *el= item->element_index(i);
-    Item_cache *tmp;
-    if (!(tmp= values[i]= el->get_cache(thd)))
+
+    if ((!values[i]) && !(values[i]= el->get_cache(thd)))
       return 1;
-    tmp->setup(thd, el);
+
+    values[i]->setup(thd, el);
   }
   return 0;
 }

sql/item.h

@@ -6901,6 +6901,9 @@ class Item_cache: public Item_fixed_hybrid,
   }
 
   virtual void keep_array() {}
+#ifndef DBUG_OFF
+  bool is_array_kept() { return TRUE; }
+#endif
   virtual void print(String *str, enum_query_type query_type);
   bool eq_def(const Field *field) 
   { 
@@ -7388,13 +7391,15 @@ class Item_cache_row: public Item_cache
   bool null_inside();
   void bring_value();
   void keep_array() { save_array= 1; }
+#ifndef DBUG_OFF
+  bool is_array_kept() { return save_array; }
+#endif
+
   void cleanup()
   {
     DBUG_ENTER("Item_cache_row::cleanup");
     Item_cache::cleanup();
-    if (save_array)
-      bzero(values, item_count*sizeof(Item**));
-    else
+    if (!save_array)
       values= 0;
     DBUG_VOID_RETURN;
   }

sql/item_cmpfunc.cc

@@ -1298,9 +1298,22 @@ bool Item_in_optimizer::fix_left(THD *thd)
     ref0= &(((Item_in_subselect *)args[1])->left_expr);
     args[0]= ((Item_in_subselect *)args[1])->left_expr;
   }
-  if ((*ref0)->fix_fields_if_needed(thd, ref0) ||
-      (!cache && !(cache= (*ref0)->get_cache(thd))))
+  if ((*ref0)->fix_fields_if_needed(thd, ref0))
     DBUG_RETURN(1);
+  if (!cache)
+  {
+    Query_arena *arena, backup;
+    arena= thd->activate_stmt_arena_if_needed(&backup);
+
+    bool rc= !(cache= (*ref0)->get_cache(thd));
+
+    if (arena)
+      thd->restore_active_arena(arena, &backup);
+
+    if (rc)
+      DBUG_RETURN(1);
+    cache->keep_array();
+  }
   /*
     During fix_field() expression could be substituted.
     So we copy changes before use
@@ -1663,19 +1676,10 @@ longlong Item_in_optimizer::val_int()
 }
 
 
-void Item_in_optimizer::keep_top_level_cache()
-{
-  cache->keep_array();
-  save_cache= 1;
-}
-
-
 void Item_in_optimizer::cleanup()
 {
   DBUG_ENTER("Item_in_optimizer::cleanup");
   Item_bool_func::cleanup();
-  if (!save_cache)
-    cache= 0;
   expr_cache= 0;
   DBUG_VOID_RETURN;
 }

sql/item_cmpfunc.h

@@ -353,8 +353,7 @@ class Item_in_optimizer: public Item_bool_func
 protected:
   Item_cache *cache;
   Item *expr_cache;
-  bool save_cache;
-  /* 
+  /*
     Stores the value of "NULL IN (SELECT ...)" for uncorrelated subqueries:
       UNKNOWN - "NULL in (SELECT ...)" has not yet been evaluated
       FALSE   - result is FALSE
@@ -364,7 +363,7 @@ class Item_in_optimizer: public Item_bool_func
 public:
   Item_in_optimizer(THD *thd, Item *a, Item *b):
     Item_bool_func(thd, a, b), cache(0), expr_cache(0),
-    save_cache(0), result_for_null_param(UNKNOWN)
+    result_for_null_param(UNKNOWN)
   { m_with_subquery= true; }
   bool fix_fields(THD *, Item **);
   bool fix_left(THD *thd);
@@ -375,7 +374,6 @@ class Item_in_optimizer: public Item_bool_func
   enum Functype functype() const   { return IN_OPTIMIZER_FUNC; }
   const char *func_name() const { return "<in_optimizer>"; }
   Item_cache **get_cache() { return &cache; }
-  void keep_top_level_cache();
   Item *transform(THD *thd, Item_transformer transformer, uchar *arg);
   virtual Item *expr_cache_insert_transformer(THD *thd, uchar *unused);
   bool is_expensive_processor(void *arg);

sql/item_subselect.cc

@@ -1994,7 +1994,7 @@ Item_in_subselect::single_value_transformer(JOIN *join)
     thd->lex->current_select= current;
 
     /* We will refer to upper level cache array => we have to save it for SP */
-    optimizer->keep_top_level_cache();
+    DBUG_ASSERT(optimizer->get_cache()[0]->is_array_kept());
 
     /*
       As far as  Item_in_optimizer does not substitute itself on fix_fields
@@ -2391,7 +2391,7 @@ Item_in_subselect::row_value_transformer(JOIN *join)
     }
 
     // we will refer to upper level cache array => we have to save it in PS
-    optimizer->keep_top_level_cache();
+    DBUG_ASSERT(optimizer->get_cache()[0]->is_array_kept());
 
     thd->lex->current_select= current;
     /*