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

[Boris FELD]

On 04/10/2018 19:24, Martin von Zweigbergk via Mercurial-devel wrote:
>
>
> On Thu, Oct 4, 2018 at 7:44 AM Boris Feld <boris.feld at octobus.net
> <mailto:boris.feld at octobus.net>> wrote:
>
>     # HG changeset patch
>     # User Boris Feld <boris.feld at octobus.net
>     <mailto: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.
We have sent a V5 series that fixes the tests, it was caused by the
condition that was `>` instead of `>=`
>  
>
>     +
>          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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