[PATCH 06 of 10 V4] context: introduce an `isintroducedafter` method and use it in copies

[Martin von Zweigbergk]

On Thu, Oct 4, 2018 at 7:44 AM Boris Feld <boris.feld at octobus.net> wrote:

> # HG changeset patch
> # User Boris Feld <boris.feld at octobus.net>
> # Date 1536252767 14400
> #      Thu Sep 06 12:52:47 2018 -0400
> # Node ID 1ef29e4089dde437729f46bb6b8acb451e11a7f5
> # Parent  36a3f6fc8dbd727e1369fb29c5bda044a9b44754
> # EXP-Topic copy-perf
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r
> 1ef29e4089dd
> context: introduce an `isintroducedafter` method and use it in copies
>
> Right now, copy tracing make effort to not traverse the graph too much to
> save
> performance. It uses a "limit" acting as a floor revision past which data
> are
> no longer relevant to the current copy tracing.
>
> However, to enforce this limit, it uses a call to `filectx.rev()`, that
> call
> can trigger a graph traversal on its own. That extra graph traversal is
> unaware of the current limit and can become very expensive. That cost is
> increased by the nature of work done in adjust link rev, we are not only
> walking down the graph, we are also checking the affected file for each
> revision we walk through. Something significantly more expensive than the
> walk
> itself.
>
> To work around this we need to make the `filectx` operation aware of the
> current limit. The first step is to introduce a dedicated method:
> `isintroducedafter`. We'll then rework that method logic to stop traversal
> as
> soon as possible.
>
> diff --git a/mercurial/context.py b/mercurial/context.py
> --- a/mercurial/context.py
> +++ b/mercurial/context.py
> @@ -767,6 +767,12 @@ class basefilectx(object):
>              # result is crash somewhere else at to some point.
>          return lkr
>
> +    def isintroducedafter(self, changelogrev):
> +        """True if a filectx have been introduced after a given floor
> revision
> +        """
> +        return (self.linkrev() > changelogrev
> +                or self.introrev() > changelogrev)
>

test-mv-cp-st-diff.t and test-mq-merge.t fail with this patch. I assume
it's because .rev() in copies.py changed to .introrev() here, but I haven't
confirmed that.


> +
>      def introrev(self):
>          """return the rev of the changeset which introduced this file
> revision
>
> diff --git a/mercurial/copies.py b/mercurial/copies.py
> --- a/mercurial/copies.py
> +++ b/mercurial/copies.py
> @@ -139,7 +139,7 @@ def _tracefile(fctx, am, limit=-1):
>      for f in fctx.ancestors():
>          if am.get(f.path(), None) == f.filenode():
>              return f
> -        if limit >= 0 and f.linkrev() < limit and f.rev() < limit:
> +        if limit >= 0 and not f.isintroducedafter(limit):
>              return None
>
>  def _dirstatecopies(d, match=None):
>
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