Allow READ_RECORD to make use of RAII and free itself on destruction

sql/records.h

@@ -27,6 +27,10 @@ class SQL_SELECT;
 class Copy_field;
 class SORT_INFO;
 
+struct READ_RECORD;
+
+void end_read_record(READ_RECORD *info);
+
 /**
   A context for reading through a single table using a chosen access method:
   index read, scan, etc, use of cache, etc.
@@ -73,7 +77,8 @@ struct READ_RECORD
   Copy_field *copy_field;
   Copy_field *copy_field_end;
 public:
-  READ_RECORD() {}
+  READ_RECORD() : table(NULL), cache(NULL) {}
+  ~READ_RECORD() { end_read_record(this); }
 };
 
 bool init_read_record(READ_RECORD *info, THD *thd, TABLE *reg_form,
@@ -82,7 +87,6 @@ bool init_read_record(READ_RECORD *info, THD *thd, TABLE *reg_form,
                       bool print_errors, bool disable_rr_cache);
 bool init_read_record_idx(READ_RECORD *info, THD *thd, TABLE *table,
                           bool print_error, uint idx, bool reverse);
-void end_read_record(READ_RECORD *info);
 
 void rr_unlock_row(st_join_table *tab);