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datapack: remove delta reuse

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Summary:
This code that reused deltas if the delta parent wasn't available was bugged
because it meant you could end up with a cycle in the delta chains. This was an
old optimization from before trees had history, so let's drop the optimization
(since trees now have history and can be correctly repacked).

Test Plan:
Ran repack on a packfile that previously caused cycles. Verified the
new version did not with `hg debugdatapack foo.datapack'

Reviewers: #mercurial

Subscribers: mjpieters

Differential Revision: https://phabricator.intern.facebook.com/D4724520
This commit is contained in:
Durham Goode 2017-03-18 19:38:45 -07:00
parent efed1f1209
commit 63f4fa69a0
3 changed files with 10 additions and 14 deletions
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12
remotefilelog/repack.py
View File

@ -332,20 +332,16 @@ class repacker(object):
deltabases[p2] = node
# Compute delta
# TODO: Optimize the deltachain fetching. Since we're
# iterating over the different version of the file, we may
# be fetching the same deltachain over and over again.
# TODO: reuse existing deltas if it matches our deltabase
if deltabase != nullid:
deltabasetext = self.data.get(filename, deltabase)
original = self.data.get(filename, node)
delta = mdiff.textdiff(deltabasetext, original)
else:
# TODO: Optimize the deltachain fetching. Since we're
# iterating over the different version of the file, we may
# be fetching the same deltachain over and over again.
chain = self.data.getdeltachain(filename, node)
x, x, deltabasename, deltabase, delta = chain[0]
if deltabasename != filename:
deltabase = nullid
delta = self.data.get(filename, node)
delta = self.data.get(filename, node)
# TODO: don't use the delta if it's larger than the fulltext
# TODO: don't use the delta if the chain is already long

6
tests/test-remotefilelog-repack-fast.t
View File

@ -232,13 +232,13 @@
# Test repacking datapack without history
$ rm -rf $CACHEDIR/master/packs/*hist*
$ hg repack
$ hg debugdatapack $TESTTMP/hgcache/master/packs/1c6261363473d5595d26728c201e1395d39bf94e
$ hg debugdatapack $TESTTMP/hgcache/master/packs/60ed975b3589fc9708a374155083fbdc7da397cb
x
Node Delta Base Delta Length
1bb2e6237e03 000000000000 8
aee31534993a d4a3ed9310e5 12
d4a3ed9310e5 1bb2e6237e03 12
aee31534993a 000000000000 4
d4a3ed9310e5 000000000000 6
y
Node Delta Base Delta Length

6
tests/test-remotefilelog-repack.t
View File

@ -231,13 +231,13 @@
# Test repacking datapack without history
$ rm -rf $CACHEDIR/master/packs/*hist*
$ hg repack
$ hg debugdatapack $TESTTMP/hgcache/master/packs/1c6261363473d5595d26728c201e1395d39bf94e
$ hg debugdatapack $TESTTMP/hgcache/master/packs/60ed975b3589fc9708a374155083fbdc7da397cb
x
Node Delta Base Delta Length
1bb2e6237e03 000000000000 8
aee31534993a d4a3ed9310e5 12
d4a3ed9310e5 1bb2e6237e03 12
aee31534993a 000000000000 4
d4a3ed9310e5 000000000000 6
y
Node Delta Base Delta Length