mercurial-scm/hg-stable: mercurial/revlogutils/deltas.py comparison

comparison mercurial/revlogutils/deltas.py @ 51345:02cc19f4f091

delta-find: move pre-filtering of candidates in its own function This organise the code further and open the way to specialization via sub-classing. Something important for the coming changes.

author	Pierre-Yves David <pierre-yves.david@octobus.net>
date	Thu, 23 Nov 2023 04:21:07 +0100
parents	d0d869fccd20
children	898c212e1b2f

comparison

equal deleted inserted replaced

-:d0d869fccd20
+:02cc19f4f091
 # before general delta, there is only one possible delta base
 yield (self.target_rev - 1,)
 yield None
 return
-deltalength = self.revlog.length
-deltaparent = self.revlog.deltaparent
-sparse = self.revlog.delta_config.sparse_revlog
 good = None
-deltas_limit = self.textlen * LIMIT_DELTA2TEXT
 group_chunk_size = self.revlog.delta_config.candidate_group_chunk_size
 tested = self.tested  # prefetch for speed and code compactness
 candidates = self._refined_groups()
 while True:
 temptative = candidates.send(good)
 if temptative is None:
 break
-group = []
+group = self._pre_filter_candidate_revs(temptative)
-for rev in temptative:
-# skip over empty delta (no need to include them in a chain)
-while not (rev == nullrev or rev in tested or deltalength(rev)):
-tested.add(rev)
-rev = deltaparent(rev)
-# no need to try a delta against nullrev, this will be done as
-# a last resort.
-if rev == nullrev:
-continue
-# filter out revision we tested already
-if rev in tested:
-continue
-# an higher authority deamed the base unworthy (e.g. censored)
-if (
-self.excluded_bases is not None
-and rev in self.excluded_bases
-):
-tested.add(rev)
-continue
-# We are in some recomputation cases and that rev is too high
-# in the revlog
-if self.target_rev is not None and rev >= self.target_rev:
-tested.add(rev)
-continue
-# filter out delta base that will never produce good delta
-#
-# if the delta of that base is already bigger than the limit
-# for the delta chain size, doing a delta is hopeless.
-if deltas_limit < self.revlog.length(rev):
-tested.add(rev)
-continue
-if sparse and self.revlog.rawsize(rev) < (
-self.textlen // LIMIT_BASE2TEXT
-):
-tested.add(rev)
-continue
-# no delta for rawtext-changing revs (see "candelta" for why)
-if self.revlog.flags(rev) & REVIDX_RAWTEXT_CHANGING_FLAGS:
-tested.add(rev)
-continue
-# If we reach here, we are about to build and test a delta.
-# The delta building process will compute the chaininfo in all
-# case, since that computation is cached, it is fine to access
-# it here too.
-chainlen, chainsize = self.revlog._chaininfo(rev)
-# if chain will be too long, skip base
-if (
-self.revlog.delta_config.max_chain_len
-and chainlen >= self.revlog.delta_config.max_chain_len
-):
-tested.add(rev)
-continue
-# if chain already have too much data, skip base
-if deltas_limit < chainsize:
-tested.add(rev)
-continue
-if (
-sparse
-and self.revlog.delta_config.upper_bound_comp is not None
-):
-maxcomp = self.revlog.delta_config.upper_bound_comp
-basenotsnap = (self.p1, self.p2, nullrev)
-if rev not in basenotsnap and self.revlog.issnapshot(rev):
-snapshotdepth = self.revlog.snapshotdepth(rev)
-# If text is significantly larger than the base, we can
-# expect the resulting delta to be proportional to the size
-# difference
-revsize = self.revlog.rawsize(rev)
-rawsizedistance = max(self.textlen - revsize, 0)
-# use an estimate of the compression upper bound.
-lowestrealisticdeltalen = rawsizedistance // maxcomp
-# check the absolute constraint on the delta size
-snapshotlimit = self.textlen >> snapshotdepth
-if snapshotlimit < lowestrealisticdeltalen:
-# delta lower bound is larger than accepted upper
-# bound
-tested.add(rev)
-continue
-# check the relative constraint on the delta size
-revlength = self.revlog.length(rev)
-if revlength < lowestrealisticdeltalen:
-# delta probable lower bound is larger than target
-# base
-tested.add(rev)
-continue
-group.append(rev)
 if group:
 # When the size of the candidate group is big, it can result in
 # a quite significant performance impact. To reduce this, we
 # can send them in smaller batches until the new batch does not
 # provide any improvements.
 good = yield tuple(sub_group)
 if prev_good == good:
 break
 yield None
+def _pre_filter_candidate_revs(self, temptative):
+"""filter possible candidate before computing a delta
+This function use various criteria to pre-filter candidate delta base
+before we compute a delta and evaluate its quality.
+Such pre-filter limit the number of computed delta, an expensive operation.
+return the updated list of revision to test
+"""
+deltalength = self.revlog.length
+deltaparent = self.revlog.deltaparent
+deltas_limit = self.revinfo.textlen * LIMIT_DELTA2TEXT
+sparse = self.revlog.delta_config.sparse_revlog
+tested = self.tested
+group = []
+for rev in temptative:
+# skip over empty delta (no need to include them in a chain)
+while not (rev == nullrev or rev in tested or deltalength(rev)):
+tested.add(rev)
+rev = deltaparent(rev)
+# no need to try a delta against nullrev, this will be done as
+# a last resort.
+if rev == nullrev:
+continue
+# filter out revision we tested already
+if rev in tested:
+continue
+# an higher authority deamed the base unworthy (e.g. censored)
+if self.excluded_bases is not None and rev in self.excluded_bases:
+tested.add(rev)
+continue
+# We are in some recomputation cases and that rev is too high
+# in the revlog
+if self.target_rev is not None and rev >= self.target_rev:
+tested.add(rev)
+continue
+# filter out delta base that will never produce good delta
+#
+# if the delta of that base is already bigger than the limit
+# for the delta chain size, doing a delta is hopeless.
+if deltas_limit < self.revlog.length(rev):
+tested.add(rev)
+continue
+# if the revision we test again is too small, the resulting delta
+# will be large anyway as that amount of data to be added is big
+if sparse and self.revlog.rawsize(rev) < (
+self.textlen // LIMIT_BASE2TEXT
+):
+tested.add(rev)
+continue
+# no delta for rawtext-changing revs (see "candelta" for why)
+if self.revlog.flags(rev) & REVIDX_RAWTEXT_CHANGING_FLAGS:
+tested.add(rev)
+continue
+# If we reach here, we are about to build and test a delta.
+# The delta building process will compute the chaininfo in all
+# case, since that computation is cached, it is fine to access
+# it here too.
+chainlen, chainsize = self.revlog._chaininfo(rev)
+# if chain will be too long, skip base
+if (
+self.revlog.delta_config.max_chain_len
+and chainlen >= self.revlog.delta_config.max_chain_len
+):
+tested.add(rev)
+continue
+# if chain already have too much data, skip base
+if deltas_limit < chainsize:
+tested.add(rev)
+continue
+if sparse and self.revlog.delta_config.upper_bound_comp is not None:
+maxcomp = self.revlog.delta_config.upper_bound_comp
+basenotsnap = (self.p1, self.p2, nullrev)
+if rev not in basenotsnap and self.revlog.issnapshot(rev):
+snapshotdepth = self.revlog.snapshotdepth(rev)
+# If text is significantly larger than the base, we can
+# expect the resulting delta to be proportional to the size
+# difference
+revsize = self.revlog.rawsize(rev)
+rawsizedistance = max(self.textlen - revsize, 0)
+# use an estimate of the compression upper bound.
+lowestrealisticdeltalen = rawsizedistance // maxcomp
+# check the absolute constraint on the delta size
+snapshotlimit = self.textlen >> snapshotdepth
+if snapshotlimit < lowestrealisticdeltalen:
+# delta lower bound is larger than accepted upper
+# bound
+tested.add(rev)
+continue
+# check the relative constraint on the delta size
+revlength = self.revlog.length(rev)
+if revlength < lowestrealisticdeltalen:
+# delta probable lower bound is larger than target
+# base
+tested.add(rev)
+continue
+group.append(rev)
+return group
 def _refined_groups(self):
 good = None
 # First we try to reuse a the delta contained in the bundle.  (or from
 # the source revlog)

Mercurial > public > mercurial-scm > hg-stable

comparison mercurial/revlogutils/deltas.py @ 51345:02cc19f4f091