[PATCH STABLE] hgweb: cache fctx.parents() in annotate command (issue5414)

[Yuya Nishihara]

On Fri, 04 Nov 2016 23:07:21 -0700, Gregory Szorc wrote:
> # HG changeset patch
> # User Gregory Szorc <gregory.szorc at gmail.com>
> # Date 1478325927 25200
> #      Fri Nov 04 23:05:27 2016 -0700
> # Branch stable
> # Node ID b0dc7dd87fc8b5efee6e6d8c0bcc6ddfa52d6df3
> # Parent  e5cc44ea12de681d971fcbebb65a7fb71fd1c3c7
> hgweb: cache fctx.parents() in annotate command (issue5414)

Looks good, but one nit.

> --- a/mercurial/hgweb/webcommands.py
> +++ b/mercurial/hgweb/webcommands.py
> @@ -861,12 +861,25 @@ def annotate(web, req, tmpl):
>      f = fctx.path()
>      parity = paritygen(web.stripecount)
>  
> +    # parents() is called once per line and several lines likely belong to
> +    # same revision. So it is worth caching.
> +    # TODO there are still redundant operations within basefilectx.parents()
> +    # that could also be cached.
> +    parentscache = {}
>      def parents(f):
> -        for p in f.parents():
> -            yield {
> -                "node": p.hex(),
> -                "rev": p.rev(),
> -            }
> +        rev = f.rev()
> +        if rev in parentscache:
> +            for entry in parentscache[rev]:
> +                yield entry
> +        else:
> +            parentscache[rev] = []
> +            for p in f.parents():
> +                entry = {
> +                    'node': p.hex(),
> +                    'rev': p.rev(),
> +                }
> +                parentscache[rev].append(entry)
> +                yield entry

If the generator is stopped at the first yield, parentscache would be
incomplete.