[Kde-pim] mixedmaildir optimization suggestion

[Andras Mantia]

Kevin Krammer wrote:

> On Thursday, 2012-09-20, Andras Mantia wrote:
> 
>> The cache itself is not invalidated automatically. The purpose of the
>> cache was to limit the number of file stats (QFile::exists()) calls.
>> Items can go into the cache if:
>> - findRealKey is called on them, and they are not yet in the cache
>> - the cache is completely refreshed (this runs two entryLists() calls and
>> puts all files from cur and new into the cache)
>> - items are copied/moved inside the resource with the Maildir lib methods
>> 
>> There is no automatic comparision of the cache time with the directory
>> time, as that would involve a stat call, defeating the purpose of the
>> cache.
> 
> Then I had a very wrong understanding of the how the cache works. My
> impression was that it only speeds up operations but does never report
> invalid data.
> 
> I would prefer to have a mode of libmaildir that lets it work properly by
> itself, e.g. as described above.
> 
> stat'ing just the directory for consistency check should still be way
> faster than stat'ing every file but would keep the API work in the way it
> was intended to.

Sorry, I don't understand when would you stat the directory. Stating when it 
changes? For that you need to watch it, but if you watch, why stat?
Stating at every findRealKey()? Then we didn't won anything.

It would probably be possible to move the directory watching into the 
maildir lib, if that is what you want. Not that straightforward though, the 
watching needs to be disabled before certain operations are performed, we 
would have one watcher object per maildir folder, we need to forward the 
"dirty" signal to the resource, as that is used not only for cache, but for 
other things in the resource.

Patches are welcome, or you/we can work on it at the sprint, although I have 
some other plans for it. ;)

Andras
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András Manția | andras.mantia at kdab.com | Senior Software Engineer
Klarälvdalens Datakonsult AB, a KDAB Group company
Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
KDAB - Qt Experts - Platform-independent software solutions
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