Re: GSoC - Some questions on the idea of

From: Jeff King <peff@peff.net>
Date: Apr 11, 2012, 22:09 UTC
Message-ID: <20120411220955.GB28199@sigill.intra.peff.net>
In-Reply-To: <4F85B17E.4080005@gmail.com>

On Wed, Apr 11, 2012 at 11:29:50AM -0500, Neal Kreitzinger wrote:

Show 6 quoted lines

> How do I check the history size of a binary?  IOW, how to I check the
> size of the sum of all the delta-compressions and root blob of a binary?
>  That way I can sample different binary types to get a symptomatic idea
> of how well they are delta compressing.  I suspect that compiled
> binaries will compress well (efficient history) and graphics files may
> not compress well (large history).

I don't think there is a simple command to do it. You have to correlate blobs at a given path with objects in the packs yourself. You can script it like:

  # get the delta stats from every pack; you only need to do this part
  # once for a given history state. And obviously you would want to
  # repack before doing it.
  for i in .git/objects/pack/*.pack; do
    git verify-pack -v $i;
  done |
  perl -lne '
    # format is: sha1 type size size-in-pack offset; pick out only the
    # thing we care about: size in pack
    /^([0-9a-f]{40}) \S+\s+\d+ (\d+)/ and print "$1 $2";
  ' |
  sort >delta-stats

  # then you can do this for every path you are interested in.

  # First, get the list of blobs at that path (and follow renames, too).
  # The second line is picking the "after" sha1 from the --raw output.
  git log --follow --raw --no-abbrev $path |
  perl -lne '/:\S+ \S+ \S{40} (\S{40})/ and print $1' |
  sort -u >blobs

  # Then find the delta stats for those blobs
  join blobs delta-stats

which should give you the stored size of each version of a file.

-Peff