[MERGE] Enable caching of negative revision lookups in RemoteRepository write locks when no _real_repository has been constructed.

[Robert Collins]

On Wed, 2009-04-29 at 17:26 -0400, John Arbash Meinel wrote:
> John Arbash Meinel has voted tweak.
> Status is now: Conditionally approved
> Comment:
>           if self._real_repository is None:
> +            self._unstacked_provider.missing_keys.clear()
>               self.bzrdir._ensure_real()
>               self._set_real_repository(
>                   self.bzrdir._real_bzrdir.open_repository())
> 
> ^- Don't you need to call 
> self._unstacked_provider.enable_cache(cache_misses=True) at this point?

We already have a populated cache; enable_cache clears it. Clearing the
missing keys isn't quite enough - I'll follow up with a patch to caching
provider to allow a 'disable_cache_misses' method.


> I'm not 100% sure about this one:
>       def insert_stream(self, stream, src_format, resume_tokens):
>           target = self.target_repo
> +        target._unstacked_provider.missing_keys.clear()
>           if target._lock_token:
>               verb = 'Repository.insert_stream_locked'
>               extra_args = (target._lock_token or '',)
> 
> 
> Though my guess is that you wouldn't have to stop caching misses as long 
> as _real_repo isn't invoked yet. You could even get away with looping 
> over the stream and only removing ones that are seen, but this is 
> certainly simpler.

Long term we may do that, but its more work today, and not directly
beneficial.

-Rob
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