view mercurial/node.py @ 40419:634b45317459 stable

changegroup: restore default node ordering (issue6001)

Changeset db5501d9 changed the default node ordering from "storage" to
"linearize".

While the new API is more explicit and cleaner, the "linearize" order is
problematic on certain repositories like netbeans where it makes bundling
slower the more nodes we bundle.

Pushing and pulling 100 changesets was ~20% slower and pushing and pulling
1000 changesets was ~600% slower.

A very quick analysis of profile traces showed that the pull operation was
taking more time creating the delta.

Putting back the old default order seems to be the safe option. With more time
during the next cycle, we can understand better the impact of sorting with the
DAG order by default, the source of the regression and how to mitigate it.

/!\ We are still waiting for the full performance impact but with this patch,
bundling and pulling locally (not on the performance workstation) 1000
changesets on the netbeans repository is as fast as before the regression.

Differential Revision: https://phab.mercurial-scm.org/D5196

# node.py - basic nodeid manipulation for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# 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

import binascii

# This ugly style has a noticeable effect in manifest parsing
hex = binascii.hexlify
# Adapt to Python 3 API changes. If this ends up showing up in
# profiles, we can use this version only on Python 3, and forward
# binascii.unhexlify like we used to on Python 2.
def bin(s):
    try:
        return binascii.unhexlify(s)
    except binascii.Error as e:
        raise TypeError(e)

nullrev = -1
# In hex, this is '0000000000000000000000000000000000000000'
nullid = b"\0" * 20
nullhex = hex(nullid)

# Phony node value to stand-in for new files in some uses of
# manifests.
# In hex, this is '2121212121212121212121212121212121212121'
newnodeid = '!!!!!!!!!!!!!!!!!!!!'
# In hex, this is '3030303030303030303030303030306164646564'
addednodeid = '000000000000000added'
# In hex, this is '3030303030303030303030306d6f646966696564'
modifiednodeid = '000000000000modified'

wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}

# pseudo identifiers for working directory
# (they are experimental, so don't add too many dependencies on them)
wdirrev = 0x7fffffff
# In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
wdirid = b"\xff" * 20
wdirhex = hex(wdirid)

def short(node):
    return hex(node[:6])