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revlog: make compressed size comparisons consistent...
revlog: make compressed size comparisons consistent revlog.compress() compares the compressed size to the input size and throws away the compressed data if it is larger than the input. This is the correct thing to do, as storing compressed data that is larger than the input takes up more storage space and makes reading slower. However, the comparison was implemented inconsistently. For the streaming compression mode, we threw away the result if it was greater than or equal to the input size. But for the one-shot compression, we threw away the compression only if it was greater than the input size! This patch changes the comparison for the simple case so it is consistent with the streaming case. As a few tests demonstrate, this adds 1 byte to some revlog entries. This is because of an added 'u' header on the chunk. It seems somewhat wrong to increase the revlog size here. However, IMO the cost of 1 byte in storage is insignificant compared to the performance gains of avoiding decompression. This patch should invite questions around the heuristic for throwing away compressed data. For example, I'd argue we should be more liberal about rejecting compressed data, additionally doing so where the number of bytes saved fails to reach a threshold. But we can have this discussion another time.

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pushkey.py
61 lines | 1.7 KiB | text/x-python | PythonLexer
# pushkey.py - dispatching for pushing and pulling keys
#
# Copyright 2010 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
from . import (
bookmarks,
encoding,
obsolete,
phases,
)
def _nslist(repo):
n = {}
for k in _namespaces:
n[k] = ""
if not obsolete.isenabled(repo, obsolete.exchangeopt):
n.pop('obsolete')
return n
_namespaces = {"namespaces": (lambda *x: False, _nslist),
"bookmarks": (bookmarks.pushbookmark, bookmarks.listbookmarks),
"phases": (phases.pushphase, phases.listphases),
"obsolete": (obsolete.pushmarker, obsolete.listmarkers),
}
def register(namespace, pushkey, listkeys):
_namespaces[namespace] = (pushkey, listkeys)
def _get(namespace):
return _namespaces.get(namespace, (lambda *x: False, lambda *x: {}))
def push(repo, namespace, key, old, new):
'''should succeed iff value was old'''
pk = _get(namespace)[0]
return pk(repo, key, old, new)
def list(repo, namespace):
'''return a dict'''
lk = _get(namespace)[1]
return lk(repo)
encode = encoding.fromlocal
decode = encoding.tolocal
def encodekeys(keys):
"""encode the content of a pushkey namespace for exchange over the wire"""
return '\n'.join(['%s\t%s' % (encode(k), encode(v)) for k, v in keys])
def decodekeys(data):
"""decode the content of a pushkey namespace from exchange over the wire"""
result = {}
for l in data.splitlines():
k, v = l.split('\t')
result[decode(k)] = decode(v)
return result