view tests/test-single-head.t @ 42743:8c9a6adec67a

rust-discovery: using the children cache in add_missing

The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.

The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.

This is a case where staying on the same side of the interface
between the two languages has clear benefits.

On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.

For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:

Rust version with simple iteration
  addcommons: 57.287us
  first undecided computation: 184.278334ms
  first children cache computation: 131.056us
  addmissings iteration: 42.766us
  first addinfo total: 185.24 ms

Python + C version
  first addcommons: 0.29 ms
  addcommons 0.21 ms
  first undecided computation 191.35 ms
  addmissings 45.75 ms
  first addinfo total: 237.77 ms

On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:

Rust version:
  first undecided computation: 293.842629ms
  first children cache computation: 407.911297ms
  addmissings iteration: 34.312869ms
  first addinfo total: 776.02 ms
  taking initial sample
  query 2: sampling time: 1318.38 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings: 143.062us

Python + C version:
  first undecided computation 298.13 ms
  addmissings 80.13 ms
  first addinfo total: 399.62 ms
  taking initial sample
  query 2: sampling time: 3957.23 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings 52.88 ms

Differential Revision: https://phab.mercurial-scm.org/D6428

=====================
Test workflow options
=====================

  $ . "$TESTDIR/testlib/obsmarker-common.sh"

Test single head enforcing - Setup
=============================================

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > evolution = all
  > EOF
  $ hg init single-head-server
  $ cd single-head-server
  $ cat <<EOF >> .hg/hgrc
  > [phases]
  > publish = no
  > [experimental]
  > single-head-per-branch = yes
  > EOF
  $ mkcommit ROOT
  $ mkcommit c_dA0
  $ cd ..

  $ hg clone single-head-server client
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

Test single head enforcing - with branch only
---------------------------------------------

  $ cd client

continuing the current defaultbranch

  $ mkcommit c_dB0
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

creating a new branch

  $ hg up 'desc("ROOT")'
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg branch branch_A
  marked working directory as branch branch_A
  (branches are permanent and global, did you want a bookmark?)
  $ mkcommit c_aC0
  $ hg push --new-branch
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)

Create a new head on the default branch

  $ hg up 'desc("c_dA0")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit c_dD0
  created new head
  $ hg push -f
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  transaction abort!
  rollback completed
  abort: rejecting multiple heads on branch "default"
  (2 heads: 286d02a6e2a2 9bf953aa81f6)
  [255]

remerge them

  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ mkcommit c_dE0
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files

Test single head enforcing - after rewrite
------------------------------------------

  $ mkcommit c_dF0
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  $ hg commit --amend -m c_dF1
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 1 files (+1 heads)
  1 new obsolescence markers
  obsoleted 1 changesets

Check it does to interfer with strip
------------------------------------

setup

  $ hg branch branch_A --force
  marked working directory as branch branch_A
  $ mkcommit c_aG0
  created new head
  $ hg update 'desc("c_dF1")'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit c_dH0
  $ hg update 'desc("c_aG0")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ mkcommit c_aI0
  $ hg log -G
  @    changeset:   10:49003e504178
  |\   branch:      branch_A
  | |  tag:         tip
  | |  parent:      8:a33fb808fb4b
  | |  parent:      3:840af1c6bc88
  | |  user:        test
  | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | |  summary:     c_aI0
  | |
  | | o  changeset:   9:fe47ea669cea
  | | |  parent:      7:99a2dc242c5d
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_dH0
  | | |
  | o |  changeset:   8:a33fb808fb4b
  | |/   branch:      branch_A
  | |    user:        test
  | |    date:        Thu Jan 01 00:00:00 1970 +0000
  | |    summary:     c_aG0
  | |
  | o  changeset:   7:99a2dc242c5d
  | |  parent:      5:6ed1df20edb1
  | |  user:        test
  | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | |  summary:     c_dF1
  | |
  | o    changeset:   5:6ed1df20edb1
  | |\   parent:      4:9bf953aa81f6
  | | |  parent:      2:286d02a6e2a2
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_dE0
  | | |
  | | o  changeset:   4:9bf953aa81f6
  | | |  parent:      1:134bc3852ad2
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_dD0
  | | |
  o | |  changeset:   3:840af1c6bc88
  | | |  branch:      branch_A
  | | |  parent:      0:ea207398892e
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_aC0
  | | |
  | o |  changeset:   2:286d02a6e2a2
  | |/   user:        test
  | |    date:        Thu Jan 01 00:00:00 1970 +0000
  | |    summary:     c_dB0
  | |
  | o  changeset:   1:134bc3852ad2
  |/   user:        test
  |    date:        Thu Jan 01 00:00:00 1970 +0000
  |    summary:     c_dA0
  |
  o  changeset:   0:ea207398892e
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     ROOT
  

actual stripping

  $ hg strip --config extensions.strip= --rev 'desc("c_dH0")'
  saved backup bundle to $TESTTMP/client/.hg/strip-backup/fe47ea669cea-a41bf5a9-backup.hg