Re: metadatabase

On Sun, 12 Oct 2003 11:04:55 +0200, Ralf Engels <[email protected]> wrote:

> Hi,
> I am just trying to clean up playlist and playlistmanager.
> Some things are still missing but I have some questions to the meta 
> handling:
>
> 1. We have a playlist format (PLM) that stores meta informations. Why do 
> we need a special database for this.
>
> 2. We already have a metadatabase (mdb) why do we need another (database 
> musiccatalog) ?
>
> Can we please agree on the future stategy?
>
> I know that Kristian is in favour of his database. In principle I think 
> that using a database is a good idea. Just not in this case.
>
> I would prefere using PLM and MDB for the future. The principle is sound 
> and the implementation (expecially mdb) is quite good.
>
> BR,
> Ralf

Hi,

I've been using the new database structure mdb for a while now and I agree 
that its seems well thought out and should be what zinf uses for accessing 
metadata. However, I have come across a number of issues with it that I 
think should be resolved.


First off, the new database seems to take a random view of when to ignore 
case and when not too. For instance, My Music now lists both 'doves' and 
'Doves' as artists, yet they both have exactly the same tracks. In fact 
they both have an album called 'lost souls' and an album called 'Lost 
Souls' which both also have exactly the same tracks in.

It appears that when importing file metadata it takes case into account 
when deciding if to add a new artist/album, yet when searching for tracks 
in these artists it dosn't take case into account. I would of thought that 
it should ignore case at all times.


Next, reading metadata about a particular track seems to have got rather 
slow for a lot of my tracks. From the output from zinf it appears that as 
a lot of my tracks don't have full tags (most of them are missing the year 
tag for instance), metadata is being read from the database, then when not 
all tags have been found its reading the metadata in the file again, only 
to find once again that the tag is missing as the file hasn't actually 
changed.

I thought one of the reasons that we had the metadata stored in a database 
was so that we didn't have to keep spending time reading the metadata from 
the file whenever we needed it. The idea of looking for the extra metadata 
in another place when you can't find it in one is a good idea, but the 
current implementation seems extreamly inefficient.

Perhaps the database should store a file modified time as well as the 
other metadata, and only bother reading the metadata from the file again 
if this has changed. This, or some other idea, really needs to implemented 
as otherwise the browser can seem quite unresponsive while waiting for 
metadata.

Come to think of it, when the MusicBrainzDB is finally implemented, it is 
also likely going to take time when requesting metadata from the servers. 
So perhaps we need some common way of dealing with slow metadata sources.

Maybe the readMetadata call should return immediatly with the information 
 from the database only, and start off threads for the other metadata 
sources to read metadata from. Then when all the metadata sources return, 
a event can be triggered that causes the browser/player to re-read the 
metadata and get the now cached metadata from all sources.

Exactly how such a system is implemented obviously needs quite a bit more 
thought but it seems a resonable idea to me in principle.


Finally, it would make sense if the readEntries function could not only 
return the files and dirs in a directory, but could be made to read all 
tracks recursively in all the sub-dirs as well. This is really just a 
feature request that I will probably end up implementing my self 
eventually, but I just thought I'd mention in case anyone else wants to 
have a go. This would really be useful in enabling the browser to add 
entire dir trees to the playlist.


Anyway, all in all I think the new mdb should be the standard way that 
metadata is cached/read in zinf from now on.

David

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