tests/test-debugcommands.t

commands: add debugdeltachain command

We have debug commands for displaying overall revlog statistics
(debugrevlog) and for dumping a revlog index (debugindex). As part
of investigating various aspects of revlog behavior and performance,
I found it important to have an understanding of how revlog
delta chains behave in practice.

This patch implements a "debugdeltachain" command. For each revision
in a revlog, it dumps information about the delta chain. Which delta
chain it is part of, length of the delta chain, distance since base
revision, info about base revision, size of the delta chain, etc. The
generic formatting facility is used, which means we can templatize
output and get machine readable output like JSON.

This command has already uncovered some weird history in
mozilla-central I didn't know about. So I think it's valuable.

  $ cat << EOF >> $HGRCPATH
  > [format]
  > usegeneraldelta=yes
  > EOF

  $ hg init debugrevlog
  $ cd debugrevlog
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ hg debugrevlog -m
  format : 1
  flags  : inline, generaldelta
  
  revisions     :  1
      merges    :  0 ( 0.00%)
      normal    :  1 (100.00%)
  revisions     :  1
      full      :  1 (100.00%)
      deltas    :  0 ( 0.00%)
  revision size : 44
      full      : 44 (100.00%)
      deltas    :  0 ( 0.00%)
  
  avg chain length  : 0
  max chain length  : 0
  compression ratio : 0
  
  uncompressed data size (min/max/avg) : 43 / 43 / 43
  full revision size (min/max/avg)     : 44 / 44 / 44
  delta size (min/max/avg)             : 0 / 0 / 0

Test debugindex, with and without the --debug flag
  $ hg debugindex a
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0       3   ....       0 b789fdd96dc2 000000000000 000000000000 (re)
  $ hg --debug debugindex a
     rev    offset  length  ..... linkrev nodeid                                   p1                                       p2 (re)
       0         0       3   ....       0 b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000 (re)
  $ hg debugindex -f 1 a
     rev flag   offset   length     size  .....   link     p1     p2       nodeid (re)
       0 0000        0        3        2   ....      0     -1     -1 b789fdd96dc2 (re)
  $ hg --debug debugindex -f 1 a
     rev flag   offset   length     size  .....   link     p1     p2                                   nodeid (re)
       0 0000        0        3        2   ....      0     -1     -1 b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 (re)

debugdelta chain basic output

  $ hg debugdeltachain -m
      rev  chain# chainlen     prev   delta       size    rawsize  chainsize     ratio   lindist extradist extraratio
        0       1        1       -1    base         44         43         44   1.02326        44         0    0.00000

  $ hg debugdeltachain -m -T '{rev} {chainid} {chainlen}\n'
  0 1 1

  $ hg debugdeltachain -m -Tjson
  [
   {
    "chainid": 1,
    "chainlen": 1,
    "chainratio": 1.02325581395,
    "chainsize": 44,
    "compsize": 44,
    "deltatype": "base",
    "extradist": 0,
    "extraratio": 0.0,
    "lindist": 44,
    "prevrev": -1,
    "rev": 0,
    "uncompsize": 43
   }
  ]

Test max chain len
  $ cat >> $HGRCPATH << EOF
  > [format]
  > maxchainlen=4
  > EOF

  $ printf "This test checks if maxchainlen config value is respected also it can serve as basic test for debugrevlog -d <file>.\n" >> a
  $ hg ci -m a
  $ printf "b\n" >> a
  $ hg ci -m a
  $ printf "c\n" >> a
  $ hg ci -m a
  $ printf "d\n" >> a
  $ hg ci -m a
  $ printf "e\n" >> a
  $ hg ci -m a
  $ printf "f\n" >> a
  $ hg ci -m a
  $ printf 'g\n' >> a
  $ hg ci -m a
  $ printf 'h\n' >> a
  $ hg ci -m a
  $ hg debugrevlog -d a
  # rev p1rev p2rev start   end deltastart base   p1   p2 rawsize totalsize compression heads chainlen
      0    -1    -1     0   ???          0    0    0    0     ???      ????           ?     1        0 (glob)
      1     0    -1   ???   ???          0    0    0    0     ???      ????           ?     1        1 (glob)
      2     1    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        2 (glob)
      3     2    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        3 (glob)
      4     3    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        4 (glob)
      5     4    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        0 (glob)
      6     5    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        1 (glob)
      7     6    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        2 (glob)
      8     7    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        3 (glob)
  $ cd ..

Test internal debugstacktrace command

  $ cat > debugstacktrace.py << EOF
  > from mercurial.util import debugstacktrace, dst, sys
  > def f():
  >     dst('hello world')
  > def g():
  >     f()
  >     debugstacktrace(skip=-5, f=sys.stdout)
  > g()
  > EOF
  $ python debugstacktrace.py
  hello world at:
   debugstacktrace.py:7 in * (glob)
   debugstacktrace.py:5 in g
   debugstacktrace.py:3 in f
  stacktrace at:
   debugstacktrace.py:7 *in * (glob)
   debugstacktrace.py:6 *in g (glob)
   */util.py:* in debugstacktrace (glob)