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

[John Arbash Meinel]

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Robert Collins wrote:
> 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 think I meant "enable_cache(cache_misses=False)", so yeah, some sort
of 'know we need to stop caching misses', whether that is a separate
function or not.

> 
>> 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

John
=:->
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