Method mark_as_const

sql/sql_string.h:197–197

  inline void length(uint32 len) { str_length=len ; }
  inline bool is_empty() const { return (str_length == 0); }
  inline void mark_as_const() { Alloced_length= 0;}
  inline const char *ptr() const { return Ptr; }
  inline char *c_ptr()
  {