Re: [PATCH] describe: Don’t look up commits with --exact-match

Anders Kaseorg wrote:

On Fri, 3 Dec 2010, Jonathan Nieder wrote:

quoted

Instead of looking up the commit to be matched exactly in the commits
hash table, this makes a linear search.

[...]

I don’t think it’s ever a problem: in my repository with 1800 tags on a 
warm cache, that loop accounts for about 0.1% of even the fastest 
non-exact-match query (a commit right after a tag).

Thanks for checking.  Makes sense.

quoted

quoted

-	for_each_ref(get_name, NULL);
+	for_each_rawref(get_name, NULL);

Orthogonal change snuck in?

This does fall under the category of “Don’t lookup commits,” and is 
necessary to get the speedup (otherwise for_each_ref has already looked up 
the commits that the rest of the patch is trying to avoid looking up).  

Depends on what "Don't lookup commits" means, I suppose.  I
think the difference between _ref and _rawref is

      if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN)) {
            if (entry->flag & REF_BROKEN)
                  return 0; /* ignore dangling symref */
            if (!has_sha1_file(entry->sha1)) {
                  error("%s does not point to a valid object!", entry->name);
                  return 0;
            }
      }

so if I understand correctly, for_each_ref would still allow one to
get away without unpacking the objects.  Is that correct?