Followup to fix for bug#6050: fix valgrind warnings.

sql/item.cc

@@ -379,6 +379,12 @@ Item_field::Item_field(THD *thd, Field *f)
       orig_db_name= thd->strdup(db_name);
     orig_table_name= thd->strdup(table_name);
     orig_field_name= thd->strdup(field_name);
+    /*
+      We don't restore 'name' in cleanup because it's not changed
+      during execution. Still we need it to point to persistent
+      memory if this item is to be reused.
+    */
+    name= (char*) orig_field_name;
   }
   set_field(f);
 }
@@ -406,6 +412,20 @@ void Item_field::set_field(Field *field_par)
   fixed= 1;
 }
 
+
+/*
+  Reset this item to point to a field from the new temporary table.
+  This is used when we create a new temporary table for each execution
+  of prepared statement.
+*/
+
+void Item_field::reset_field(Field *f)
+{
+  set_field(f);
+  /* 'name' is pointing at field->field_name of old field */
+  name= (char*) f->field_name;
+}
+
 const char *Item_ident::full_name() const
 {
   char *tmp;

sql/item.h

@@ -348,6 +348,7 @@ public:
 
 class Item_field :public Item_ident
 {
+  void set_field(Field *field);
 public:
   Field *field,*result_field;
 
@@ -369,7 +370,7 @@ public:
   /*
     If this constructor is used, fix_fields() won't work, because
     db_name, table_name and column_name are unknown. It's necessary to call
-    set_field() before fix_fields() for all fields created this way.
+    reset_field() before fix_fields() for all fields created this way.
   */
   Item_field(Field *field);
   enum Type type() const { return FIELD_ITEM; }
@@ -381,7 +382,7 @@ public:
   longlong val_int_result();
   String *str_result(String* tmp);
   bool send(Protocol *protocol, String *str_arg);
-  void set_field(Field *field);
+  void reset_field(Field *f);
   bool fix_fields(THD *, struct st_table_list *, Item **);
   void make_field(Send_field *tmp_field);
   int save_in_field(Field *field,bool no_conversions);

sql/sql_union.cc

@@ -360,7 +360,7 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
       {
         Item_field *item_field= (Item_field*) it++;
         DBUG_ASSERT(item_field);
-        item_field->set_field(*field);
+        item_field->reset_field(*field);
       }
     }
   }