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revlog: choose best delta for parentdelta (issue2466)

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When parentdelta is enabled, we choose the delta that has the minimum
distance to its base. Otherwise, base may be sufficiently far away to
require a full version, resulting in greatly reduced compression.
This commit is contained in:
Matt Mackall 2010-10-30 02:47:34 -05:00
parent d0eecfc8e5
commit 90141f6021
1 changed files with 7 additions and 8 deletions
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15
mercurial/revlog.py
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@ -1194,15 +1194,14 @@ class revlog(object):
d = None
p1r, p2r = self.rev(p1), self.rev(p2)
if self._parentdelta:
deltarev, deltanode = p1r, p1
flags = REVIDX_PARENTDELTA
else:
deltarev, deltanode = prev, self.node(prev)
# should we try to build a delta?
if deltarev != nullrev:
d = builddelta(deltarev)
if prev != nullrev:
d = builddelta(prev)
if self._parentdelta and prev != p1r:
d2 = builddelta(p1r)
if d2 < d:
d = d2
flags = REVIDX_PARENTDELTA
dist, l, data, base = d
# full versions are inserted when the needed deltas