[DaveBlake]

If my sources are for instance
/media/audioplay/comedy
/media/audioplay/audiobooks
is it ok to add a single path node
/media/audioplay/
or should it better be a multipath source of the single sources above?

Having a music source with a single parent folder, and then other music sources with subfolders is fine.
 

Would adding the sourceid filter option for musicdb://years,genres and recentlies speed up things?

It is still about me redesigning the way SQL queries are built for all the filtering variations, more than how "fetch me the genres for songs on this source" is specified using filter type node (with rules and group) or folder type node (with db url and options).

 

Filter type queries on genre by path are slow as hell

Filter type nodes on artists with source or path or genre rules that are grouped by genre are seriously flawed. It is the <group>genres</group> that causes some very ugly SQL to be generated when combined with rules that do not apply directly to fields of the artist table e.g. source, path and genre all mean looking at the songs/albums of the artists.

 

Folder type queries work for every item that allows sourceid filtering (artists, albums). A list of possible filter options for folder type queries (musicdb://...) would be glorious @Dave!

Folder type nodes is an undocumented feature
It takes advantage of how screen navigation historically works internally, but I think the long term plan was to remove that type of node entirely. Using the options on folder type nodes for filtering was useful accident rather than design. However don't worry, not going to happen until the filter type nodes (which do offer much greater filtering possibilites) can support all the navigation behaviour that folder type nodes offer. My work is to achieve that and then there will be no need for users to use folder type nodes, they will be able to get what they want with the much clearer filter type.