The usage statistics [kactivities, baloo, ktp, plasma]

[Vishesh Handa]

On Tue, Oct 21, 2014 at 11:22 AM, Ivan Čukić <ivan.cukic at kde.org> wrote:

> One thing to ask here is if baloo skips indexing a file that is in an
> indexable folder - does it store any info about the file (name, date etc.)
> or
> not?
>

No. It does store any info.

Still, baloo is not off the hook - if we want to detect the file moving and
> deletion (as suggested by the guy behind baloo :P), at least for the
> indexed
> files, we need baloo to somehow tell us what was moved/deleted.
>
> This could be implemented in a few different ways that would all have some
> drawbacks:
> 1 - baloo sending signals - big drawback would be that if the clients miss
> out
> an event, the database would become inconsistent;
> 2 - saving baloo ids along files in kamd - drawback is that baloo becomes
> tied
> to sqlite (as you mentioned);
> 3 - baloo saving information about what has moved/deleted so that a client
> can
> ask for all events that happened since some timestamp - drawbacks here are
> that the clients need to regularly check for the updates meaning they will
> most likely have at least a bit out of date information
>

The NTFS file system has something similar. It's called a USN Journal. It's
their solution to applications being able to see what changed when they
weren't running or if they missed some events.

I'm not too keen on Baloo doing stuff like this, but we can make something
new which does stuff like this, and (possibly) make Baloo use it.

I looked into the BTRFS file system about a month ago, and we could
hypothetically use its snapshot feature to know what has changed since a
particular time interval. Currently btfs-send, sending both the data and
the metadata, but that can be improved. I'm not saying that we make btrfs a
dependency for Plasma, I'm just throwing ideas out there which was can use
IF the user is on btrfs.


> 4 - combination of 1 and 3 - it would be the most complex implementation,
> but
> it would work properly (distributed dbs are evil  )
>
> And, an additional problem is what to do about the files that are not
> indexed
> by baloo? Should it silently fail or what? For the statistics, it would be
> (imo) ok to fail silently, but for activity linking, it might be nice to
> show
> a warning message to the user.
>

Be careful here.

* Silently failing is not always a good idea
* Making file Indexing mandatory for statistics also seems a little bit
risky.

-- 
Vishesh Handa
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