view tests/test-narrow-update.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

  $ . "$TESTDIR/narrow-library.sh"

create full repo

  $ hg init master
  $ cd master
  $ echo init > init
  $ hg ci -Aqm 'initial'

  $ mkdir inside
  $ echo inside > inside/f1
  $ mkdir outside
  $ echo outside > outside/f1
  $ hg ci -Aqm 'add inside and outside'

  $ echo modified > inside/f1
  $ hg ci -qm 'modify inside'

  $ echo modified > outside/f1
  $ hg ci -qm 'modify outside'

  $ cd ..

  $ hg clone --narrow ssh://user@dummy/master narrow --include inside
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 2 changes to 1 files
  new changesets *:* (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow
  $ hg debugindex -c
     rev linkrev nodeid       p1           p2
       0       0 9958b1af2add 000000000000 000000000000
       1       1 2db4ce2a3bfe 9958b1af2add 000000000000
       2       2 0980ee31a742 2db4ce2a3bfe 000000000000
       3       3 4410145019b7 0980ee31a742 000000000000

  $ hg update -q 0

Can update to revision with changes inside

  $ hg update -q 'desc("add inside and outside")'
  $ hg update -q 'desc("modify inside")'
  $ find *
  inside
  inside/f1
  $ cat inside/f1
  modified

Can update to revision with changes outside

  $ hg update -q 'desc("modify outside")'
  $ find *
  inside
  inside/f1
  $ cat inside/f1
  modified

Can update with a deleted file inside

  $ hg rm inside/f1
  $ hg update -q 'desc("modify inside")'
  $ hg update -q 'desc("modify outside")'
  $ hg update -q 'desc("initial")'
  $ hg update -q 'desc("modify inside")'

Can update with a moved file inside

  $ hg mv inside/f1 inside/f2
  $ hg update -q 'desc("modify outside")'
  $ hg update -q 'desc("add inside and outside")'
  $ hg update -q 'desc("modify inside")'