Re: [Tracker] Merging Turtle branch to Trunk

[Ivan Frade <ivan frade nokia com>]

Hi!

 Thanks Martyn for the review. I'll try to clarify how this
backup/restore metadata works.

> Summary:
>
> It looks to me like a lot of work is still needed to keep the code clean 
> and consistent with the current code base. There are a couple of leaks 
> which need fixing and a couple of issues which this patch fixes too. The 
> major concern I have is about when the restore and backup are actually 
> done. Unless I have misunderstood (which is entirely possible) it seems 
> they are done at the wrong times, or at least could be done at better times.

Ok, The goal here is to save the data set by the user (e.g.
User:Keywords, Audio:Playcount).

How is trackerd working now on reindex:

1) trackerd is started with --force-reindex
2) trackerd start tracker-db-manager with FORCE_REINDEX flag to remove
all the DB files
3) trackerd starts crawling and sending the uris to the indexer


How i want to plug the save/restore functionality:

1) trackerd is started with --force-reindex
2) trackerd starts the tracker-db-manager (without the force reindex
flag because we need to READ the Dbs)
  2.1) trackerd reads the metadata from the user
  2.2) trackerd save those metadata to a turtle file
  2.3) trackerd closes the db stack.
  2.4) trackerd install a callback to detect the Finished signal from
the indexer.
3) trackerd start tracker-db-manager with FORCE_REINDEX flag to remove
all the DB files
4) trackerd starts crawling and sending the uris to the indexer
5) when the "Finished" signal comes, call the "_restore_backup" method
in the indexer.


 Why are we restoring the backup AFTER indexing the files?
1) To ignore metadata of files that are not anymore in the filesystem
2) To overwrite default values coming from the extractor

 [Also note that we cannot set metadata of files that are not yet in the
DB so we need to crawl first]


 So, we need to save the data BEFORE deleting the DBs and restore it
AFTER finished the crawling. It is not perfect but any other solution
requires deep changes in the starting sequence (and probably
tracker-db-manager).

 Comments are welcome,

Ivan