/*
    * Tools for estimating how large a chunk of shared memory will be needed
    * to store a TOC and its dependent objects.  Note: we don't really support
    * large numbers of keys, but it's convenient to declare number_of_keys
    * as a Size anyway.
    */
   typedef struct
   {
   	Size		space_for_chunks;
   	Size		number_of_keys;
   } shm_toc_estimator;