view tests/test-parseindex.t @ 42222:57203e0210f8

copies: calculate mergecopies() based on pathcopies()

When copies are stored in changesets, we need a changeset-centric
version of mergecopies() just like we have a changeset-centric version
of pathcopies(). I think the natural way of thinking about
mergecopies() is in terms of pathcopies() from the base to each of the
commits. So if we can rewrite mergecopies() based on two such
pathcopies() calls, we'll get the changeset-centric version for
free. That's what this patch does.

A nice bonus is that it ends up being a lot simpler. mergecopies() has
accumulated a lot of technical debt over time. One good example is the
code for dealing with grafts (the "partial/incomplete/dirty"
stuff). Since pathcopies() already deals with backwards renames and
ping-pong renames, we get that for free.

I've run tests with hard-coded debug logging for "fullcopy" and while
I haven't looked at every difference it produces, all the ones I have
looked at seemed reasonable to me. I'm a little surprised that no more
tests fail when run with '--extra-config-opt
experimental.copies.read-from=compatibility' compared to before this
patch. This patch also fixes the broken cases in test-annotate.t and
test-fastannotate.t. It also enables the part of test-copies.t that
was previously disabled exactly because mergecopies() needed to get a
changeset-centric version.

One drawback of the rewritten code is that we may now make
remotefilelog prefetch more files. We used to prefetch files that were
unique to either side of the merge compared to the other. We now
prefetch files that are unique to either side of the merge compared to
the base. This means that if you added the same file to each side, we
would not prefetch it before, but we would now. Such cases are
probably quite rare, but one likely scenario where they happen is when
moving from a commit to its successor (or the other way around). The
user will probably already have the files in the cache in such cases,
so it's probably not a big deal.

Some timings for calculating mergecopies between two revisions
(revisions shown on each line, all using the common ancestor as base):

In the hg repo:
4.8 4.9: 0.21s -> 0.21s
4.0 4.8: 0.35s -> 0.63s

In and old copy of the mozilla-unified repo:
FIREFOX_BETA_60_BASE^ FIREFOX_BETA_60_BASE: 0.82s -> 0.82s
FIREFOX_NIGHTLY_59_END FIREFOX_BETA_60_BASE: 2.5s -> 2.6s
FIREFOX_BETA_59_END FIREFOX_BETA_60_BASE: 3.9s -> 4.1s
FIREFOX_AURORA_50_BASE FIREFOX_BETA_60_BASE: 31s -> 33s

So it's measurably slower in most cases. The most significant
difference is in the hg repo between revisions 4.0 and 4.8. In that
case it seems to come from the fact that pathcopies() uses
fctx.isintroducedafter() (in _tracefile), while the old mergecopies()
used fctx.linkrev() (in _checkcopies()). That results in a single call
to filectx._adjustlinkrev(), which is responsible for the entire
difference in time (in my repo). So we pay a performance penalty but
we get more correct code (see change in
test-mv-cp-st-diff.t). Deleting the "== f.filenode()" in _tracefile()
recovers the lost performance in the hg repo.

There were are few other optimizations in _checkcopies() that I could
not measure any impact from. One was from the "seen" set. Another was
from a "continue" when the file was not in the destination manifest
(corresponding to "am" in _tracefile).

Also note that merge copies are not calculated when updating with a
clean working copy, which is probably the most common case. I
therefore think the much simpler code is worth the slowdown.

Differential Revision: https://phab.mercurial-scm.org/D6255

revlog.parseindex must be able to parse the index file even if
an index entry is split between two 64k blocks.  The ideal test
would be to create an index file with inline data where
64k < size < 64k + 64 (64k is the size of the read buffer, 64 is
the size of an index entry) and with an index entry starting right
before the 64k block boundary, and try to read it.
We approximate that by reducing the read buffer to 1 byte.

  $ hg init a
  $ cd a
  $ echo abc > foo
  $ hg add foo
  $ hg commit -m 'add foo'
  $ echo >> foo
  $ hg commit -m 'change foo'
  $ hg log -r 0:
  changeset:   0:7c31755bf9b5
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add foo
  
  changeset:   1:26333235a41c
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change foo
  
  $ cat >> test.py << EOF
  > from __future__ import print_function
  > from mercurial import changelog, node, pycompat, vfs
  > 
  > class singlebyteread(object):
  >     def __init__(self, real):
  >         self.real = real
  > 
  >     def read(self, size=-1):
  >         if size == 65536:
  >             size = 1
  >         return self.real.read(size)
  > 
  >     def __getattr__(self, key):
  >         return getattr(self.real, key)
  > 
  >     def __enter__(self):
  >         self.real.__enter__()
  >         return self
  > 
  >     def __exit__(self, *args, **kwargs):
  >         return self.real.__exit__(*args, **kwargs)
  > 
  > def opener(*args):
  >     o = vfs.vfs(*args)
  >     def wrapper(*a, **kwargs):
  >         f = o(*a, **kwargs)
  >         return singlebyteread(f)
  >     return wrapper
  > 
  > cl = changelog.changelog(opener(b'.hg/store'))
  > print(len(cl), 'revisions:')
  > for r in cl:
  >     print(pycompat.sysstr(node.short(cl.node(r))))
  > EOF
  $ "$PYTHON" test.py
  2 revisions:
  7c31755bf9b5
  26333235a41c

  $ cd ..

#if no-pure

Test SEGV caused by bad revision passed to reachableroots() (issue4775):

  $ cd a

  $ "$PYTHON" <<EOF
  > from __future__ import print_function
  > from mercurial import changelog, vfs
  > cl = changelog.changelog(vfs.vfs(b'.hg/store'))
  > print('good heads:')
  > for head in [0, len(cl) - 1, -1]:
  >     print('%s: %r' % (head, cl.reachableroots(0, [head], [0])))
  > print('bad heads:')
  > for head in [len(cl), 10000, -2, -10000, None]:
  >     print('%s:' % head, end=' ')
  >     try:
  >         cl.reachableroots(0, [head], [0])
  >         print('uncaught buffer overflow?')
  >     except (IndexError, TypeError) as inst:
  >         print(inst)
  > print('good roots:')
  > for root in [0, len(cl) - 1, -1]:
  >     print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root])))
  > print('out-of-range roots are ignored:')
  > for root in [len(cl), 10000, -2, -10000]:
  >     print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root])))
  > print('bad roots:')
  > for root in [None]:
  >     print('%s:' % root, end=' ')
  >     try:
  >         cl.reachableroots(root, [len(cl) - 1], [root])
  >         print('uncaught error?')
  >     except TypeError as inst:
  >         print(inst)
  > EOF
  good heads:
  0: [0]
  1: [0]
  -1: []
  bad heads:
  2: head out of range
  10000: head out of range
  -2: head out of range
  -10000: head out of range
  None: an integer is required( .got type NoneType.)? (re)
  good roots:
  0: [0]
  1: [1]
  -1: [-1]
  out-of-range roots are ignored:
  2: []
  10000: []
  -2: []
  -10000: []
  bad roots:
  None: an integer is required( .got type NoneType.)? (re)

  $ cd ..

Test corrupted p1/p2 fields that could cause SEGV at parsers.c:

  $ mkdir invalidparent
  $ cd invalidparent

  $ hg clone --pull -q --config phases.publish=False ../a limit --config format.sparse-revlog=no
  $ hg clone --pull -q --config phases.publish=False ../a neglimit --config format.sparse-revlog=no
  $ hg clone --pull -q --config phases.publish=False ../a segv --config format.sparse-revlog=no
  $ rm -R limit/.hg/cache neglimit/.hg/cache segv/.hg/cache

  $ "$PYTHON" <<EOF
  > data = open("limit/.hg/store/00changelog.i", "rb").read()
  > poisons = [
  >     (b'limit', b'\0\0\0\x02'),
  >     (b'neglimit', b'\xff\xff\xff\xfe'),
  >     (b'segv', b'\0\x01\0\0'),
  > ]
  > for n, p in poisons:
  >     # corrupt p1 at rev0 and p2 at rev1
  >     d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:]
  >     open(n + b"/.hg/store/00changelog.i", "wb").write(d)
  > EOF

  $ hg -R limit debugrevlogindex -f1 -c
     rev flag     size   link     p1     p2       nodeid
       0 0000       62      0      2     -1 7c31755bf9b5
       1 0000       65      1      0      2 26333235a41c

  $ hg -R limit debugdeltachain -c
      rev  chain# chainlen     prev   delta       size    rawsize  chainsize     ratio   lindist extradist extraratio
        0       1        1       -1    base         63         62         63   1.01613        63         0    0.00000
        1       2        1       -1    base         66         65         66   1.01538        66         0    0.00000

  $ hg -R neglimit debugrevlogindex -f1 -c
     rev flag     size   link     p1     p2       nodeid
       0 0000       62      0     -2     -1 7c31755bf9b5
       1 0000       65      1      0     -2 26333235a41c

  $ hg -R segv debugrevlogindex -f1 -c
     rev flag     size   link     p1     p2       nodeid
       0 0000       62      0  65536     -1 7c31755bf9b5
       1 0000       65      1      0  65536 26333235a41c

  $ hg -R segv debugdeltachain -c
      rev  chain# chainlen     prev   delta       size    rawsize  chainsize     ratio   lindist extradist extraratio
        0       1        1       -1    base         63         62         63   1.01613        63         0    0.00000
        1       2        1       -1    base         66         65         66   1.01538        66         0    0.00000

  $ cat <<EOF > test.py
  > from __future__ import print_function
  > import sys
  > from mercurial import changelog, pycompat, vfs
  > cl = changelog.changelog(vfs.vfs(pycompat.fsencode(sys.argv[1])))
  > n0, n1 = cl.node(0), cl.node(1)
  > ops = [
  >     ('reachableroots',
  >      lambda: cl.index.reachableroots2(0, [1], [0], False)),
  >     ('compute_phases_map_sets', lambda: cl.computephases([[0], []])),
  >     ('index_headrevs', lambda: cl.headrevs()),
  >     ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)),
  >     ('find_deepest', lambda: cl.ancestor(n0, n1)),
  >     ]
  > for l, f in ops:
  >     print(l + ':', end=' ')
  >     try:
  >         f()
  >         print('uncaught buffer overflow?')
  >     except ValueError as inst:
  >         print(inst)
  > EOF

  $ "$PYTHON" test.py limit/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range
  $ "$PYTHON" test.py neglimit/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range
  $ "$PYTHON" test.py segv/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range

  $ cd ..

#endif