view tests/test-clone-update-order.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

  $ hg init
  $ echo foo > bar
  $ hg commit -Am default
  adding bar
  $ hg up -r null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch mine
  marked working directory as branch mine
  (branches are permanent and global, did you want a bookmark?)
  $ echo hello > world
  $ hg commit -Am hello
  adding world
  $ hg up -r null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch other
  marked working directory as branch other
  $ echo good > bye
  $ hg commit -Am other
  adding bye
  $ hg up -r mine
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg clone -U -u . .#other ../b -r 0 -r 1 -r 2 -b other
  abort: cannot specify both --noupdate and --updaterev
  [255]

  $ hg clone -U .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  $ rm -rf ../b

  $ hg clone -u . .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch mine
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -u 0 .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -u 1 .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch mine
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -u 2 .#other ../b -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

Test -r mine ... mine is ignored:

  $ hg clone -u 2 .#other ../b -r mine -r 0 -r 1 -r 2 -b other
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone .#other ../b -b default -b mine
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+2 heads)
  new changesets 8c68ee086fd0:fcc393352796
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone .#other ../b
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets fcc393352796
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b

  $ hg clone -U . ../c -r 1 -r 2 > /dev/null
  $ hg clone ../c ../b
  updating to branch other
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm -rf ../b ../c