view tests/test-rebase-newancestor.t @ 44363:f7459da77f23

nodemap: introduce an option to use mmap to read the nodemap mapping

The performance and memory benefit is much greater if we don't have to copy all
the data in memory for each information. So we introduce an option (on by
default) to read the data using mmap.

This changeset is the last one definition the API for index support nodemap
data. (they have to be able to use the mmaping).

Below are some benchmark comparing the best we currently have in 5.3 with the
final step of this series (using the persistent nodemap implementation in
Rust). The benchmark run `hg perfindex` with various revset and the following
variants:

Before:

 * do not use the persistent nodemap
 * use the CPython implementation of the index for nodemap
 * use mmapping of the changelog index

After:

 * use the MixedIndex Rust code, with the NodeTree object for nodemap access
   (still in review)
 * use the persistent nodemap data from disk
 * access the persistent nodemap data through mmap
 * use mmapping of the changelog index

The persistent nodemap greatly speed up  most operation on very large
repositories. Some of the previously very fast lookup end up a bit slower because
the persistent nodemap has to be setup. However the absolute slowdown is very
small and won't matters in the big picture.

Here are some numbers (in seconds) for the reference copy of mozilla-try:

Revset            Before   After     abs-change speedup

-10000:           0.004622 0.005532   0.000910  ×   0.83
-10:              0.000050 0.000132   0.000082  ×   0.37
tip               0.000052 0.000085   0.000033  ×   0.61
0 + (-10000:)     0.028222 0.005337  -0.022885  ×   5.29
0                 0.023521 0.000084  -0.023437  × 280.01
(-10000:) + 0     0.235539 0.005308  -0.230231  ×  44.37
(-10:) + :9       0.232883 0.000180  -0.232703  ×1293.79
(-10000:) + (:99) 0.238735 0.005358  -0.233377  ×  44.55
:99 + (-10000:)   0.317942 0.005593  -0.312349  ×  56.84
:9 + (-10:)       0.313372 0.000179  -0.313193  ×1750.68
:9                0.316450 0.000143  -0.316307  ×2212.93


On smaller repositories, the cost of nodemap related operation is not as big, so
the win is much more modest. Yet it helps shaving a handful of millisecond here
and there.

Here are some numbers (in seconds) for the reference copy of mercurial:

Revset            Before   After     abs-change speedup
-10:              0.000065 0.000097   0.000032  × 0.67
tip               0.000063 0.000078   0.000015  × 0.80
0                 0.000561 0.000079  -0.000482  × 7.10
-10000:           0.004609 0.003648  -0.000961  × 1.26
0 + (-10000:)     0.005023 0.003715  -0.001307  × 1.35
(-10:) + :9       0.002187 0.000108  -0.002079  ×20.25
(-10000:) + 0     0.006252 0.003716  -0.002536  × 1.68
(-10000:) + (:99) 0.006367 0.003707  -0.002660  × 1.71
:9 + (-10:)       0.003846 0.000110  -0.003736  ×34.96
:9                0.003854 0.000099  -0.003755  ×38.92
:99 + (-10000:)   0.007644 0.003778  -0.003866  × 2.02

Differential Revision: https://phab.mercurial-scm.org/D7894

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > drawdag=$TESTDIR/drawdag.py
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
  > EOF

  $ hg init repo
  $ cd repo

  $ echo A > a
  $ echo >> a
  $ hg ci -Am A
  adding a

  $ echo B > a
  $ echo >> a
  $ hg ci -m B

  $ echo C > a
  $ echo >> a
  $ hg ci -m C

  $ hg up -q -C 0

  $ echo D >> a
  $ hg ci -Am AD
  created new head

  $ hg tglog
  @  3: 3878212183bd 'AD'
  |
  | o  2: 30ae917c0e4f 'C'
  | |
  | o  1: 0f4f7cb4f549 'B'
  |/
  o  0: 1e635d440a73 'A'
  
  $ hg rebase -s 1 -d 3
  rebasing 1:0f4f7cb4f549 "B"
  merging a
  rebasing 2:30ae917c0e4f "C"
  merging a
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/0f4f7cb4f549-82b3b163-rebase.hg

  $ hg tglog
  o  3: 25773bc4b4b0 'C'
  |
  o  2: c09015405f75 'B'
  |
  @  1: 3878212183bd 'AD'
  |
  o  0: 1e635d440a73 'A'
  

  $ cd ..


Test rebasing of merges with ancestors of the rebase destination - a situation
that often happens when trying to recover from repeated merging with a mainline
branch.

The test case creates a dev branch that contains a couple of merges from the
default branch. When rebasing to the default branch, these merges would be
merges with ancestors on the same branch. The merges _could_ contain some
interesting conflict resolutions or additional changes in the merge commit, but
that is mixed up with the actual merge stuff and there is in general no way to
separate them.

  $ hg init ancestor-merge
  $ cd ancestor-merge

  $ touch f-default
  $ hg ci -Aqm 'default: create f-default'

  $ hg branch -q dev
  $ hg ci -qm 'dev: create branch'

  $ echo stuff > f-dev
  $ hg ci -Aqm 'dev: f-dev stuff'

  $ hg up -q default
  $ echo stuff > f-default
  $ hg ci -m 'default: f-default stuff'

  $ hg up -q dev
  $ hg merge -q default
  $ hg ci -m 'dev: merge default'

  $ hg up -q default
  $ hg rm f-default
  $ hg ci -m 'default: remove f-default'

  $ hg up -q dev
  $ hg merge -q default
  $ hg ci -m 'dev: merge default'

  $ hg up -q default
  $ echo stuff > f-other
  $ hg ci -Aqm 'default: f-other stuff'

  $ hg tglog
  @  7: e08089805d82 'default: f-other stuff'
  |
  | o  6: 010ced67e558 'dev: merge default' dev
  |/|
  o |  5: 462860db70a1 'default: remove f-default'
  | |
  | o  4: 4b019212aaf6 'dev: merge default' dev
  |/|
  o |  3: f157ecfd2b6b 'default: f-default stuff'
  | |
  | o  2: ec2c14fb2984 'dev: f-dev stuff' dev
  | |
  | o  1: 1d1a643d390e 'dev: create branch' dev
  |/
  o  0: e90e8eb90b6f 'default: create f-default'
  
  $ hg clone -qU . ../ancestor-merge-2

Full rebase all the way back from branching point:

  $ hg rebase -r 'only(dev,default)' -d default --config ui.interactive=True << EOF
  > c
  > EOF
  rebasing 1:1d1a643d390e "dev: create branch"
  note: not rebasing 1:1d1a643d390e "dev: create branch", its destination already has all its changes
  rebasing 2:ec2c14fb2984 "dev: f-dev stuff"
  rebasing 4:4b019212aaf6 "dev: merge default"
  note: not rebasing 4:4b019212aaf6 "dev: merge default", its destination already has all its changes
  rebasing 6:010ced67e558 "dev: merge default"
  note: not rebasing 6:010ced67e558 "dev: merge default", its destination already has all its changes
  saved backup bundle to $TESTTMP/ancestor-merge/.hg/strip-backup/1d1a643d390e-4a6f6d17-rebase.hg
  $ hg tglog
  o  4: 3e075b1c0a40 'dev: f-dev stuff'
  |
  @  3: e08089805d82 'default: f-other stuff'
  |
  o  2: 462860db70a1 'default: remove f-default'
  |
  o  1: f157ecfd2b6b 'default: f-default stuff'
  |
  o  0: e90e8eb90b6f 'default: create f-default'
  
Grafty cherry picking rebasing:

  $ cd ../ancestor-merge-2

  $ hg phase -fdr0:
  $ hg rebase -r 'children(only(dev,default))' -d default --config ui.interactive=True << EOF
  > c
  > EOF
  rebasing 2:ec2c14fb2984 "dev: f-dev stuff"
  rebasing 4:4b019212aaf6 "dev: merge default"
  abort: rebasing 4:4b019212aaf6 will include unwanted changes from 1:1d1a643d390e
  [255]
  $ cd ..


Test order of parents of rebased merged with un-rebased changes as p1.

  $ hg init parentorder
  $ cd parentorder
  $ touch f
  $ hg ci -Aqm common
  $ touch change
  $ hg ci -Aqm change
  $ touch target
  $ hg ci -Aqm target
  $ hg up -qr 0
  $ touch outside
  $ hg ci -Aqm outside
  $ hg merge -qr 1
  $ hg ci -m 'merge p1 3=outside p2 1=ancestor'
  $ hg par
  changeset:   4:6990226659be
  tag:         tip
  parent:      3:f59da8fc0fcf
  parent:      1:dd40c13f7a6f
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     merge p1 3=outside p2 1=ancestor
  
  $ hg up -qr 1
  $ hg merge -qr 3
  $ hg ci -qm 'merge p1 1=ancestor p2 3=outside'
  $ hg par
  changeset:   5:a57575f79074
  tag:         tip
  parent:      1:dd40c13f7a6f
  parent:      3:f59da8fc0fcf
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     merge p1 1=ancestor p2 3=outside
  
  $ hg tglog
  @    5: a57575f79074 'merge p1 1=ancestor p2 3=outside'
  |\
  +---o  4: 6990226659be 'merge p1 3=outside p2 1=ancestor'
  | |/
  | o  3: f59da8fc0fcf 'outside'
  | |
  +---o  2: a60552eb93fb 'target'
  | |
  o |  1: dd40c13f7a6f 'change'
  |/
  o  0: 02f0f58d5300 'common'
  
  $ hg rebase -r 4 -d 2
  rebasing 4:6990226659be "merge p1 3=outside p2 1=ancestor"
  saved backup bundle to $TESTTMP/parentorder/.hg/strip-backup/6990226659be-4d67a0d3-rebase.hg
  $ hg tip
  changeset:   5:cca50676b1c5
  tag:         tip
  parent:      2:a60552eb93fb
  parent:      3:f59da8fc0fcf
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     merge p1 3=outside p2 1=ancestor
  
  $ hg rebase -r 4 -d 2
  rebasing 4:a57575f79074 "merge p1 1=ancestor p2 3=outside"
  saved backup bundle to $TESTTMP/parentorder/.hg/strip-backup/a57575f79074-385426e5-rebase.hg
  $ hg tip
  changeset:   5:f9daf77ffe76
  tag:         tip
  parent:      2:a60552eb93fb
  parent:      3:f59da8fc0fcf
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     merge p1 1=ancestor p2 3=outside
  
  $ hg tglog
  @    5: f9daf77ffe76 'merge p1 1=ancestor p2 3=outside'
  |\
  +---o  4: cca50676b1c5 'merge p1 3=outside p2 1=ancestor'
  | |/
  | o  3: f59da8fc0fcf 'outside'
  | |
  o |  2: a60552eb93fb 'target'
  | |
  o |  1: dd40c13f7a6f 'change'
  |/
  o  0: 02f0f58d5300 'common'
  
rebase of merge of ancestors

  $ hg up -qr 2
  $ hg merge -qr 3
  $ echo 'other change while merging future "rebase ancestors"' > other
  $ hg ci -Aqm 'merge rebase ancestors'
  $ hg rebase -d 5 -v
  rebasing 6:4c5f12f25ebe "merge rebase ancestors" (tip)
  resolving manifests
  removing other
  resolving manifests
  getting other
  committing files:
  other
  committing manifest
  committing changelog
  rebase merging completed
  1 changesets found
  uncompressed size of bundle content:
       199 (changelog)
       216 (manifests)
       182  other
  saved backup bundle to $TESTTMP/parentorder/.hg/strip-backup/4c5f12f25ebe-f46990e5-rebase.hg
  1 changesets found
  uncompressed size of bundle content:
       254 (changelog)
       167 (manifests)
       182  other
  adding branch
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  rebase completed
  $ hg tglog
  @  6: 113755df812b 'merge rebase ancestors'
  |
  o    5: f9daf77ffe76 'merge p1 1=ancestor p2 3=outside'
  |\
  +---o  4: cca50676b1c5 'merge p1 3=outside p2 1=ancestor'
  | |/
  | o  3: f59da8fc0fcf 'outside'
  | |
  o |  2: a60552eb93fb 'target'
  | |
  o |  1: dd40c13f7a6f 'change'
  |/
  o  0: 02f0f58d5300 'common'
  
Due to the limitation of 3-way merge algorithm (1 merge base), rebasing a merge
may include unwanted content:

  $ hg init $TESTTMP/dual-merge-base1
  $ cd $TESTTMP/dual-merge-base1
  $ hg debugdrawdag <<'EOS'
  >   F
  >  /|
  > D E
  > | |
  > B C
  > |/
  > A Z
  > |/
  > R
  > EOS
  $ hg rebase -r D+E+F -d Z
  rebasing 5:5f2c926dfecf "D" (D)
  rebasing 6:b296604d9846 "E" (E)
  rebasing 7:caa9781e507d "F" (F tip)
  abort: rebasing 7:caa9781e507d will include unwanted changes from 4:d6003a550c2c or 3:c1e6b162678d
  [255]

The warning does not get printed if there is no unwanted change detected:

  $ hg init $TESTTMP/dual-merge-base2
  $ cd $TESTTMP/dual-merge-base2
  $ hg debugdrawdag <<'EOS'
  >   D
  >  /|
  > B C
  > |/
  > A Z
  > |/
  > R
  > EOS
  $ hg rebase -r B+C+D -d Z
  rebasing 3:c1e6b162678d "B" (B)
  rebasing 4:d6003a550c2c "C" (C)
  rebasing 5:c8f78076273e "D" (D tip)
  saved backup bundle to $TESTTMP/dual-merge-base2/.hg/strip-backup/d6003a550c2c-6f1424b6-rebase.hg
  $ hg manifest -r 'desc(D)'
  B
  C
  R
  Z

The merge base could be different from old p1 (changed parent becomes new p1):

  $ hg init $TESTTMP/chosen-merge-base1
  $ cd $TESTTMP/chosen-merge-base1
  $ hg debugdrawdag <<'EOS'
  >   F
  >  /|
  > D E
  > | |
  > B C Z
  > EOS
  $ hg rebase -r D+F -d Z
  rebasing 3:004dc1679908 "D" (D)
  rebasing 5:4be4cbf6f206 "F" (F tip)
  saved backup bundle to $TESTTMP/chosen-merge-base1/.hg/strip-backup/004dc1679908-06a66a3c-rebase.hg
  $ hg manifest -r 'desc(F)'
  C
  D
  E
  Z
  $ hg log -r `hg log -r 'desc(F)' -T '{p1node}'` -T '{desc}\n'
  D

  $ hg init $TESTTMP/chosen-merge-base2
  $ cd $TESTTMP/chosen-merge-base2
  $ hg debugdrawdag <<'EOS'
  >   F
  >  /|
  > D E
  > | |
  > B C Z
  > EOS
  $ hg rebase -r E+F -d Z
  rebasing 4:974e4943c210 "E" (E)
  rebasing 5:4be4cbf6f206 "F" (F tip)
  saved backup bundle to $TESTTMP/chosen-merge-base2/.hg/strip-backup/974e4943c210-b2874da5-rebase.hg
  $ hg manifest -r 'desc(F)'
  B
  D
  E
  Z
  $ hg log -r `hg log -r 'desc(F)' -T '{p1node}'` -T '{desc}\n'
  E