Mercurial > hg-stable
changeset 51354:f3f35b37f4b2
delta-find: move good delta code earlier in the class
Nothing change except the code location. This greatly helps readability of the
next future diff,
| author | Pierre-Yves David <pierre-yves.david@octobus.net> |
|---|---|
| date | Sun, 07 Jan 2024 00:56:15 +0100 |
| parents | 5c0693553cb6 |
| children | 866ab9f447d4 |
| files | mercurial/revlogutils/deltas.py |
| diffstat | 1 files changed, 124 insertions(+), 124 deletions(-) [+] |
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--- a/mercurial/revlogutils/deltas.py Thu Jan 04 17:20:30 2024 +0100 +++ b/mercurial/revlogutils/deltas.py Sun Jan 07 00:56:15 2024 +0100 @@ -637,6 +637,130 @@ self._last_good = None self.current_group = self._candidates_iterator.send(self._last_good) + def is_good_delta_info(self, deltainfo): + """Returns True if the given delta is good. + + Good means that it is within the disk span, disk size, and chain length + bounds that we know to be performant. + """ + if not self._is_good_delta_info_universal(deltainfo): + return False + if not self._is_good_delta_info_chain_quality(deltainfo): + return False + if not self._is_good_delta_info_snapshot_constraints(deltainfo): + return False + return True + + def _is_good_delta_info_universal(self, deltainfo): + """Returns True if the given delta is good. + + This performs generic checks needed by all format variants. + + This is used by is_good_delta_info. + """ + + if deltainfo is None: + return False + + # the DELTA_BASE_REUSE_FORCE case should have been taken care of sooner + # so we should never end up asking such question. Adding the assert as + # a safe-guard to detect anything that would be fishy in this regard. + assert ( + self.revinfo.cachedelta is None + or self.revinfo.cachedelta[2] != DELTA_BASE_REUSE_FORCE + or not self.revlog.delta_config.general_delta + ) + + # Bad delta from new delta size: + # + # If the delta size is larger than the target text, storing the delta + # will be inefficient. + if self.revinfo.textlen < deltainfo.deltalen: + return False + + return True + + def _is_good_delta_info_chain_quality(self, deltainfo): + """Returns True if the chain associated with the delta is good. + + This performs checks for format that use delta chains. + + This is used by is_good_delta_info. + """ + # - 'deltainfo.distance' is the distance from the base revision -- + # bounding it limits the amount of I/O we need to do. + + defaultmax = self.revinfo.textlen * 4 + maxdist = self.revlog.delta_config.max_deltachain_span + if not maxdist: + maxdist = deltainfo.distance # ensure the conditional pass + maxdist = max(maxdist, defaultmax) + + # Bad delta from read span: + # + # If the span of data read is larger than the maximum allowed. + # + # In the sparse-revlog case, we rely on the associated "sparse + # reading" to avoid issue related to the span of data. In theory, it + # would be possible to build pathological revlog where delta pattern + # would lead to too many reads. However, they do not happen in + # practice at all. So we skip the span check entirely. + if ( + not self.revlog.delta_config.sparse_revlog + and maxdist < deltainfo.distance + ): + return False + + # Bad delta from cumulated payload size: + # + # - 'deltainfo.compresseddeltalen' is the sum of the total size of + # deltas we need to apply -- bounding it limits the amount of CPU + # we consume. + max_chain_data = self.revinfo.textlen * LIMIT_DELTA2TEXT + # If the sum of delta get larger than K * target text length. + if max_chain_data < deltainfo.compresseddeltalen: + return False + + # Bad delta from chain length: + # + # If the number of delta in the chain gets too high. + if ( + self.revlog.delta_config.max_chain_len + and self.revlog.delta_config.max_chain_len < deltainfo.chainlen + ): + return False + return True + + def _is_good_delta_info_snapshot_constraints(self, deltainfo): + """Returns True if the chain associated with snapshots + + This performs checks for format that use sparse-revlog and intermediate + snapshots. + + This is used by is_good_delta_info. + """ + # bad delta from intermediate snapshot size limit + # + # If an intermediate snapshot size is higher than the limit. The + # limit exist to prevent endless chain of intermediate delta to be + # created. + if ( + deltainfo.snapshotdepth is not None + and (self.revinfo.textlen >> deltainfo.snapshotdepth) + < deltainfo.deltalen + ): + return False + + # bad delta if new intermediate snapshot is larger than the previous + # snapshot + if ( + deltainfo.snapshotdepth + and self.revlog.length(deltainfo.base) < deltainfo.deltalen + ): + return False + + return True + @property def done(self): """True when all possible candidate have been tested""" @@ -1041,130 +1165,6 @@ # fulltext. yield (prev,) - def is_good_delta_info(self, deltainfo): - """Returns True if the given delta is good. - - Good means that it is within the disk span, disk size, and chain length - bounds that we know to be performant. - """ - if not self._is_good_delta_info_universal(deltainfo): - return False - if not self._is_good_delta_info_chain_quality(deltainfo): - return False - if not self._is_good_delta_info_snapshot_constraints(deltainfo): - return False - return True - - def _is_good_delta_info_universal(self, deltainfo): - """Returns True if the given delta is good. - - This performs generic checks needed by all format variants. - - This is used by is_good_delta_info. - """ - - if deltainfo is None: - return False - - # the DELTA_BASE_REUSE_FORCE case should have been taken care of sooner - # so we should never end up asking such question. Adding the assert as - # a safe-guard to detect anything that would be fishy in this regard. - assert ( - self.revinfo.cachedelta is None - or self.revinfo.cachedelta[2] != DELTA_BASE_REUSE_FORCE - or not self.revlog.delta_config.general_delta - ) - - # Bad delta from new delta size: - # - # If the delta size is larger than the target text, storing the delta - # will be inefficient. - if self.revinfo.textlen < deltainfo.deltalen: - return False - - return True - - def _is_good_delta_info_chain_quality(self, deltainfo): - """Returns True if the chain associated with the delta is good. - - This performs checks for format that use delta chains. - - This is used by is_good_delta_info. - """ - # - 'deltainfo.distance' is the distance from the base revision -- - # bounding it limits the amount of I/O we need to do. - - defaultmax = self.revinfo.textlen * 4 - maxdist = self.revlog.delta_config.max_deltachain_span - if not maxdist: - maxdist = deltainfo.distance # ensure the conditional pass - maxdist = max(maxdist, defaultmax) - - # Bad delta from read span: - # - # If the span of data read is larger than the maximum allowed. - # - # In the sparse-revlog case, we rely on the associated "sparse - # reading" to avoid issue related to the span of data. In theory, it - # would be possible to build pathological revlog where delta pattern - # would lead to too many reads. However, they do not happen in - # practice at all. So we skip the span check entirely. - if ( - not self.revlog.delta_config.sparse_revlog - and maxdist < deltainfo.distance - ): - return False - - # Bad delta from cumulated payload size: - # - # - 'deltainfo.compresseddeltalen' is the sum of the total size of - # deltas we need to apply -- bounding it limits the amount of CPU - # we consume. - max_chain_data = self.revinfo.textlen * LIMIT_DELTA2TEXT - # If the sum of delta get larger than K * target text length. - if max_chain_data < deltainfo.compresseddeltalen: - return False - - # Bad delta from chain length: - # - # If the number of delta in the chain gets too high. - if ( - self.revlog.delta_config.max_chain_len - and self.revlog.delta_config.max_chain_len < deltainfo.chainlen - ): - return False - return True - - def _is_good_delta_info_snapshot_constraints(self, deltainfo): - """Returns True if the chain associated with snapshots - - This performs checks for format that use sparse-revlog and intermediate - snapshots. - - This is used by is_good_delta_info. - """ - # bad delta from intermediate snapshot size limit - # - # If an intermediate snapshot size is higher than the limit. The - # limit exist to prevent endless chain of intermediate delta to be - # created. - if ( - deltainfo.snapshotdepth is not None - and (self.revinfo.textlen >> deltainfo.snapshotdepth) - < deltainfo.deltalen - ): - return False - - # bad delta if new intermediate snapshot is larger than the previous - # snapshot - if ( - deltainfo.snapshotdepth - and self.revlog.length(deltainfo.base) < deltainfo.deltalen - ): - return False - - return True - class SnapshotCache: __slots__ = ('snapshots', '_start_rev', '_end_rev')