annotate tests/test-sparse-revlog.t @ 39494:e72130f58f5d

snapshot: consider all snapshots in the parents' chains

There are no reasons to only consider full snapshot as a possible base for an
intermediate snapshot.  Now that the basic principles have been set, we can
start adding more levels of snapshots.

We now consider all snapshots in the parent's chains (full or intermediate).
This creates a chain of intermediate snapshots, each smaller than the previous
one.

# Effect On The Test Repository

In the test repository, we can see a decrease in the revlog size and slightly
shorter delta chain.

However, that approach creates snapshots more frequently, increasing the risk
of ending into problematic cases in very branchy repositories (not triggered
by the test repository). The next changesets will remove that risk by adding
logic that increases deltas reuse.

====================================
Test delta choice with sparse revlog
====================================

Sparse-revlog usually shows the most gain on Manifest. However, it is simpler
to general an appropriate file, so we test with a single file instead. The
goal is to observe intermediate snapshot being created.

We need a large enough file. Part of the content needs to be replaced
repeatedly while some of it changes rarely.

  $ bundlepath="$TESTDIR/artifacts/cache/big-file-churn.hg"

  $ expectedhash=`cat "$bundlepath".md5`
  $ if [ ! -f "$bundlepath" ]; then
  >     echo 'skipped: missing artifact, run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'
  >     exit 80
  > fi
  $ currenthash=`f -M "$bundlepath" | cut -d = -f 2`
  $ if [ "$currenthash" != "$expectedhash" ]; then
  >     echo 'skipped: outdated artifact, md5 "'"$currenthash"'" expected "'"$expectedhash"'" run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'
  >     exit 80
  > fi

  $ cat >> $HGRCPATH << EOF
  > [format]
  > sparse-revlog = yes
  > [storage]
  > revlog.optimize-delta-parent-choice = yes
  > EOF
  $ hg init sparse-repo
  $ cd sparse-repo
  $ hg unbundle $bundlepath
  adding changesets
  adding manifests
  adding file changes
  added 5001 changesets with 5001 changes to 1 files (+89 heads)
  new changesets 9706f5af64f4:d9032adc8114 (5001 drafts)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updated to "d9032adc8114: commit #5000"
  89 other heads for branch "default"

  $ hg log --stat -r 0:3
  changeset:   0:9706f5af64f4
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     initial commit
  
   SPARSE-REVLOG-TEST-FILE |  10500 ++++++++++++++++++++++++++++++++++++++++++++++
   1 files changed, 10500 insertions(+), 0 deletions(-)
  
  changeset:   1:724907deaa5e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #1
  
   SPARSE-REVLOG-TEST-FILE |  1068 +++++++++++++++++++++++-----------------------
   1 files changed, 534 insertions(+), 534 deletions(-)
  
  changeset:   2:62c41bce3e5d
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #2
  
   SPARSE-REVLOG-TEST-FILE |  1068 +++++++++++++++++++++++-----------------------
   1 files changed, 534 insertions(+), 534 deletions(-)
  
  changeset:   3:348a9cbd6959
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #3
  
   SPARSE-REVLOG-TEST-FILE |  1068 +++++++++++++++++++++++-----------------------
   1 files changed, 534 insertions(+), 534 deletions(-)
  

  $ f -s .hg/store/data/*.d
  .hg/store/data/_s_p_a_r_s_e-_r_e_v_l_o_g-_t_e_s_t-_f_i_l_e.d: size=63812493
  $ hg debugrevlog *
  format : 1
  flags  : generaldelta
  
  revisions     :     5001
      merges    :      625 (12.50%)
      normal    :     4376 (87.50%)
  revisions     :     5001
      empty     :        0 ( 0.00%)
                     text  :        0 (100.00%)
                     delta :        0 (100.00%)
      snapshot  :      179 ( 3.58%)
        lvl-0   :              4 ( 0.08%)
        lvl-1   :             49 ( 0.98%)
        lvl-2   :             56 ( 1.12%)
        lvl-3   :             63 ( 1.26%)
        lvl-4   :              7 ( 0.14%)
      deltas    :     4822 (96.42%)
  revision size : 63812493
      snapshot  : 10745878 (16.84%)
        lvl-0   :         804204 ( 1.26%)
        lvl-1   :        4986508 ( 7.81%)
        lvl-2   :        2858810 ( 4.48%)
        lvl-3   :        1958906 ( 3.07%)
        lvl-4   :         137450 ( 0.22%)
      deltas    : 53066615 (83.16%)
  
  chunks        :     5001
      0x78 (x)  :     5001 (100.00%)
  chunks size   : 63812493
      0x78 (x)  : 63812493 (100.00%)
  
  avg chain length  :       17
  max chain length  :       45
  max chain reach   : 27506743
  compression ratio :       27
  
  uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
  full revision size (min/max/avg)     : 201007 / 201077 / 201051
  inter-snapshot size (min/max/avg)    : 13223 / 172097 / 56809
      level-1   (min/max/avg)          : 13223 / 172097 / 101765
      level-2   (min/max/avg)          : 28558 / 85237 / 51050
      level-3   (min/max/avg)          : 14647 / 41752 / 31093
      level-4   (min/max/avg)          : 18596 / 20760 / 19635
  delta size (min/max/avg)             : 10649 / 104791 / 11005
  
  deltas against prev  : 4171 (86.50%)
      where prev = p1  : 4127     (98.95%)
      where prev = p2  :    0     ( 0.00%)
      other            :   44     ( 1.05%)
  deltas against p1    :  633 (13.13%)
  deltas against p2    :   18 ( 0.37%)
  deltas against other :    0 ( 0.00%)