I'm seeing that mercurial efficiently compresses the files in repository
(repo/.hg/store/data)
Does anybody know what kind of compression is used for repository files?
Thanks.
+1
A:
Initial versions of files are compressed using deflate (same algorithm as zip), but for updated files, Mercurial stores only a (binary) diff against a previous version.
It also tries to do the right thing: When a deflated JPEG turns out bigger than the original, it will not store it "compressed", for example.
Thilo
2009-08-13 07:13:25
It actually does a little more than that. If you *only* store deltas, the time to regenerate a stored file from the revlogs grows as a function of the number of changesets (i.e. this an O(N) algorithm). To bound that process Mercurial periodically stores the entire file *again*, and relies on the zlib compression to squash that back down to a reasonable size.
quark
2009-08-18 23:01:11
+4
A:
There are two levels of compression in Mercurial repositories: delta storage, and zlib compression.
In addition, various other parts employ also compression. For example, bundles can be compressed with both gzip and bzip2, as can archive tarballs - but I don't think you were asking for these.
Martin v. Löwis
2009-08-13 07:25:47
+2
A:
You might find Matt's paper on the revlog format interesting: http://mercurial.selenic.com/wiki/Presentations?action=AttachFile&do=view&target=ols-mercurial-paper.pdf
Steve Losh
2009-08-14 16:41:48