MDEV-33767: Memory leaks found in some tests run with --ps-protocol against a server built with the option -DWITH_PROTECT_STATEMENT_MEMROOT

Found memory leaks were introduced by the commit a896beb MDEV-18844 Implement EXCEPT ALL and INTERSECT ALL operations and caused by using a statement arena instead a runtime arena for allocation of objects having temporary life span by their nature. Aforementioned memory leaks were produced by running queries that typically use select with intersect, union or table values constructors. To fix these memory leaks use the runtime arena for allocation of Item_field objects used by set operations. Additionally, OOM handling added on allocation of aforementioned Item_field objects.

Author: dmitryshulga

sql/sql_union.cc

@@ -1263,26 +1263,21 @@ bool st_select_lex_unit::join_union_item_types(THD *thd_arg,
 }
 
 
-bool init_item_int(THD* thd, Item_int* &item)
+static bool init_item_int(THD* thd, Item_int* &item)
 {
  if (!item)
  {
- Query_arena *arena, backup_arena;
- arena= thd->activate_stmt_arena_if_needed(&backup_arena);
-
  item= new (thd->mem_root) Item_int(thd, 0);
 
- if (arena)
- thd->restore_active_arena(arena, &backup_arena);
-
  if (!item)
- return false;
+  return true;
  }
  else
  {
  item->value= 0;
  }
- return true;
+
+ return false;
 }
 
 
@@ -1762,8 +1757,12 @@ bool st_select_lex_unit::prepare(TABLE_LIST *derived_arg,
 
  for(uint i= 0; i< hidden; i++)
  {
- init_item_int(thd, addon_fields[i]);
- types.push_front(addon_fields[i]);
+ if (init_item_int(thd, addon_fields[i]) ||
+ types.push_front(addon_fields[i]))
+ {
+ types.empty();
+ goto err;
+ }
  addon_fields[i]->name.str= i ? "__CNT_1" : "__CNT_2";
  addon_fields[i]->name.length= 7;
  }