MDEV-32225 Test case from opt_tvc.test fails with statement memory protection

Memory for type holders of the columns of a table value constructor must
be allocated only once.

Approved by Oleksandr Byelkin <sanja@mariadb.com>

sql/sql_tvc.cc

@@ -227,7 +227,7 @@ bool table_value_constr::prepare(THD *thd, SELECT_LEX *sl,
   
   List_item *first_elem= li++;
   uint cnt= first_elem->elements;
-  Type_holder *holders;
+  Type_holder *holders= type_holders;
   
   if (cnt == 0)
   {
@@ -238,12 +238,14 @@ bool table_value_constr::prepare(THD *thd, SELECT_LEX *sl,
   if (fix_fields_for_tvc(thd, li))
     DBUG_RETURN(true);
 
-  if (!(holders= new (thd->stmt_arena->mem_root) Type_holder[cnt]) ||
+  if (!holders)
+  {
+    holders= type_holders= new (thd->stmt_arena->mem_root) Type_holder[cnt];
+    if (!holders ||
          join_type_handlers_for_tvc(thd, li, holders, cnt) ||
          get_type_attributes_for_tvc(thd, li, holders,
 				     lists_of_values.elements, cnt))
        DBUG_RETURN(true);
-  
     List_iterator_fast<Item> it(*first_elem);
     Item *item;
     Query_arena *arena, backup;
@@ -264,6 +266,7 @@ bool table_value_constr::prepare(THD *thd, SELECT_LEX *sl,
 
     if (unlikely(thd->is_fatal_error))
       DBUG_RETURN(true); // out of memory
+  }
     
   result= tmp_result;
   

sql/sql_tvc.h

@@ -24,6 +24,7 @@ class Explain_query;
 class Item_func_in;
 class st_select_lex_unit;
 typedef class st_select_lex SELECT_LEX;
+class Type_holder;
 
 /**
   @class table_value_constr
@@ -38,6 +39,7 @@ class table_value_constr : public Sql_alloc
   List<List_item> lists_of_values;
   select_result *result;
   SELECT_LEX *select_lex;
+  Type_holder *type_holders;
 
   enum { QEP_NOT_PRESENT_YET, QEP_AVAILABLE} have_query_plan;
 
@@ -46,7 +48,7 @@ class table_value_constr : public Sql_alloc
   
   table_value_constr(List<List_item> tvc_values, SELECT_LEX *sl,
 		     ulonglong select_options_arg) :
-    lists_of_values(tvc_values), result(0), select_lex(sl),
+    lists_of_values(tvc_values), result(0), select_lex(sl), type_holders(0),
     have_query_plan(QEP_NOT_PRESENT_YET), explain(0),
     select_options(select_options_arg)
   { };