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Compressing Revlog Delta Chunks Reusing The Zlib Stream
Status: The implementation needs to be updated for the code changes recently introduced by parent deltas.
Current revlog format compresses delta chunks separately from each other. The idea is using the same compression object for a snapshot and its delta chunks, simply sync-flushing the zlib stream for each chunk.
Test results
Mercurial crew (http://hg.intevation.org/mercurial/crew) - 10395 revisions (head: 4612cded5176 ) |
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|
total size (kb) |
relative size |
00manifest.d size (kb) |
00manifest.d relative size |
plain |
25708 |
1.00 |
8632 |
1.00 |
zlibstream applied |
18400 |
0.72 |
4104 |
0.48 |
plain, |
21740 |
0.85 |
4668 |
0.54 |
zlibstream applied, |
16856 |
0.66 |
2560 |
0.30 |
|
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Linux kernel (http://www.kernel.org/hg/index.cgi/linux-2.6/) - 181609 revisions (head: 64ef3e5df11e ) |
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|
total size (kb) |
relative size |
00manifest.d size (kb) |
00manifest.d relative size |
plain |
1418724 |
1.00 |
895624 |
1.00 |
zlibstream applied |
1343864 |
0.95 |
874396 |
0.98 |
plain, |
752248 |
0.53 |
231112 |
0.26 |
zlibstream applied, |
681380 |
0.48 |
211912 |
0.24 |
Patch queue
The code currently doesn't properly sets and checks the requires file, and the changes on revlog chunks take effect immediately on any new revisions: take care when running this on existing repositories!
http://bitbucket.org/wbruna/hg-zlibstream/
Mailing list threads
http://www.selenic.com/pipermail/mercurial-devel/2010-February/018564.html