rust-nodemap: accounting for dead blocks
By the very append-only nature of the `NodeTree`, inserting
new blocks has the effect of making some of the older ones
useless as they become unreachable.
Therefore some automatic housekeeping will need to be provided.
This is standard procedure in the word of databases, under names
such as "repack" or "vacuum".
The new `masked_readonly_blocks()` will provide callers with
useful information to decide if the nodetree is ripe for
repacking, but all the `NodeTree` can provide is how many
blocks have been masked in the currently mutable part. Analysing
the readonly part would be way too long to do it for each
transaction and defeat the whole purpose of nodemap persistence.
Serializing callers (from the Python layer) will get this figure
before each extraction and maintain an aggregate counter of
unreachable blocks separately.
Note: at this point, the most efficient repacking is just to restart
afresh with a full rescan.
Differential Revision: https://phab.mercurial-scm.org/D8097
# extension to emulate invoking 'dirstate.write()' at the time
# specified by '[fakedirstatewritetime] fakenow', only when
# 'dirstate.write()' is invoked via functions below:
#
# - 'workingctx._poststatusfixup()' (= 'repo.status()')
# - 'committablectx.markcommitted()'
from __future__ import absolute_import
from mercurial import (
context,
dirstate,
extensions,
policy,
registrar,
)
from mercurial.utils import dateutil
try:
from mercurial import rustext
rustext.__name__ # force actual import (see hgdemandimport)
except ImportError:
rustext = None
configtable = {}
configitem = registrar.configitem(configtable)
configitem(
b'fakedirstatewritetime', b'fakenow', default=None,
)
parsers = policy.importmod('parsers')
rustmod = policy.importrust('parsers')
def pack_dirstate(fakenow, orig, dmap, copymap, pl, now):
# execute what original parsers.pack_dirstate should do actually
# for consistency
actualnow = int(now)
for f, e in dmap.items():
if e[0] == 'n' and e[3] == actualnow:
e = parsers.dirstatetuple(e[0], e[1], e[2], -1)
dmap[f] = e
return orig(dmap, copymap, pl, fakenow)
def fakewrite(ui, func):
# fake "now" of 'pack_dirstate' only if it is invoked while 'func'
fakenow = ui.config(b'fakedirstatewritetime', b'fakenow')
if not fakenow:
# Execute original one, if fakenow isn't configured. This is
# useful to prevent subrepos from executing replaced one,
# because replacing 'parsers.pack_dirstate' is also effective
# in subrepos.
return func()
# parsing 'fakenow' in YYYYmmddHHMM format makes comparison between
# 'fakenow' value and 'touch -t YYYYmmddHHMM' argument easy
fakenow = dateutil.parsedate(fakenow, [b'%Y%m%d%H%M'])[0]
if rustmod is not None:
# The Rust implementation does not use public parse/pack dirstate
# to prevent conversion round-trips
orig_dirstatemap_write = dirstate.dirstatemap.write
wrapper = lambda self, st, now: orig_dirstatemap_write(
self, st, fakenow
)
dirstate.dirstatemap.write = wrapper
orig_dirstate_getfsnow = dirstate._getfsnow
wrapper = lambda *args: pack_dirstate(fakenow, orig_pack_dirstate, *args)
orig_module = parsers
orig_pack_dirstate = parsers.pack_dirstate
orig_module.pack_dirstate = wrapper
dirstate._getfsnow = lambda *args: fakenow
try:
return func()
finally:
orig_module.pack_dirstate = orig_pack_dirstate
dirstate._getfsnow = orig_dirstate_getfsnow
if rustmod is not None:
dirstate.dirstatemap.write = orig_dirstatemap_write
def _poststatusfixup(orig, workingctx, status, fixup):
ui = workingctx.repo().ui
return fakewrite(ui, lambda: orig(workingctx, status, fixup))
def markcommitted(orig, committablectx, node):
ui = committablectx.repo().ui
return fakewrite(ui, lambda: orig(committablectx, node))
def extsetup(ui):
extensions.wrapfunction(
context.workingctx, '_poststatusfixup', _poststatusfixup
)
extensions.wrapfunction(context.workingctx, 'markcommitted', markcommitted)