[PATCH] manifest: avoid intersectfiles for matches > 100 files

[Matt Mackall]

I've queued this for default with Martin's suggested message, thanks.

On Thu, 2015-03-19 at 16:50 +0000, Martin von Zweigbergk wrote:
> On Thu, Mar 19, 2015 at 9:40 AM Durham Goode <durham at fb.com> wrote:
> 
> >
> >
> > On 3/19/15 7:59 AM, Martin von Zweigbergk wrote:
> >
> >
> >
> > On Thu, Mar 19, 2015 at 7:54 AM Durham Goode <durham at fb.com> wrote:
> >
> >>  Hg histedit a few commits and change the last pick to mess.  As long as
> >> the last commit doesn't add any new files it will trigger the issue (since
> >> the issue only happens when all files being matched exist in the manifest
> >> already).
> >>
> > I agree with the fix, but if I understood correctly from our discussion on
> > IRC yesterday, the description is not accurate. Wasn't the problem rather
> > that the part after the "or" evaluates "util.all(fn in self for fn in
> > files)", which is almost the same thing as intersectfiles() and it's called
> > only to determine whether to call intersectfiles(). But if that's the case,
> > I guess I don't understand why the overall condition does not evaluate to
> > True (before your patch). Is it that all the files are not in the changeset
> > (self)?
> >
> > The problem I encountered is that the overall condition *did* evaluate to
> > true, because all the files were in self.  So it went down into
> > intersectfiles.  The description in the commit message is a little
> > different from what I encountered, but probably still an accurate case that
> > could cause the issue.
> >
> 
> Sure, it may be accurate, but so far, we don't know that it's relevant. How
> about the following, which we know is relevant?
> 
> "Previously we tried to avoid manifest.intersectfiles for exact matches
> with less than 100 files. However, when the left side of the "or" is false,
> the right side gets evaluated, of course, and the evaluation of "util.all(fn
> in self for fn in files)" is both costly in itself, and likely to be true,
> causing intersectfiles() to be called after all. Fix this by moving the
> check for less than 100 files outside of the "or" expression, thereby also
> making it apply for a non-exact matcher, should one be passed in."
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