gnus: Registry Article Refer Method

 
 9.18.2 Fetching by ‘Message-ID’ Using the Registry
 --------------------------------------------------
 
 The registry knows how to map each ‘Message-ID’ to the group it’s in.
 This can be leveraged to enhance the “article refer method”, the thing
 that tells Gnus how to look up an article given its Message-ID (See
 Finding the Parent).
 
    The ‘nnregistry’ refer method does exactly that.  It has the
 advantage that an article may be found regardless of the group it’s
 in—provided its ‘Message-ID’ is known to the registry.  It can be
 enabled by augmenting the start-up file with something along these
 lines:
 
      ;; Keep enough entries to have a good hit rate when referring to an
      ;; article using the registry.  Use long group names so that Gnus
      ;; knows where the article is.
      (setq gnus-registry-max-entries 2500)
 
      (gnus-registry-initialize)
 
      (setq gnus-refer-article-method
            '(current
              (nnregistry)
              (nnweb "gmane" (nnweb-type gmane))))
 
    The example above instructs Gnus to first look up the article in the
 current group, or, alternatively, using the registry, and finally, if
 all else fails, using Gmane.