code: func (x *Index) initDeletesCache() (err error) {
  	x.deletes = newDeletionCache()
  	it := x.queryPrefix(keyDeleted)
  	defer closeIterator(it, &err)
  	for it.Next() {
  		cl, ok := kvDeleted(it.Key())
  		if !ok {
  			return fmt.Errorf("Bogus keyDeleted entry key: want |\"deleted\"|<deleted blobref>|<reverse claimdate>|<deleter claim>|, got %q", it.Key())
  		}
  		targetDeletions := append(x.deletes.m[cl.Target],
  			deletion{
  				deleter: cl.BlobRef,
  				when:    cl.Date,
  			})
  		sort.Sort(sort.Reverse(byDeletionDate(targetDeletions)))
  		x.deletes.m[cl.Target] = targetDeletions
  	}
  	return err
  }
docs: // initDeletesCache creates and populates the deletion status cache used by the index
  // for faster calls to IsDeleted and DeletedAt. It is called by New.