While working on the DB optimisation I discovered one query which does
not follow the 'FieldQuery' interface - 'PlaylistQuery', so I looked
into it in more detail.
One special thing about it is that it uses 'IN' SQL operator, so
I defined 'InQuery' query class to have this logic outside of the
playlist context.
Otherwise, it seems like 'PlaylistQuery' is a field query, even if it
has a very special way of resolving values it wants to query. In the
future, we may want to consider moving this kind of custom
_initialisation_ logic away from '__init__' methods to
factory/@classmethod: this should make it more clear that the purpose of
such logic is to resolve the data that is required to define
a particular FieldQuery class fully.
As far as I can tell, the fast SQL path was never used before, since a
query would use the default `clause()` implementation. It is only the
`FieldQuery.clause()` that could delegate to `col_clause()`, but
`PlaylistQuery` is not a `FieldQuery`.
- Add NamedQuery abstract class to be able to express the expectation
that a query should be such a query (and have a specific constructor
signature) in construct_query_part
- slightly (and probably completely irrelevantly) improve Query.__hash__
- also, sprinkle some ABC/abstractmethod around to clarify things
Adds M3U playlist support as a query to beets and thus partially
resolves issue #123. The implementation is heavily based on #2380 by
Robin McCorkell.
It supports referencing playlists by absolute path:
$ beet ls playlist:/path/to/someplaylist.m3u
It also supports referencing playlists by name. The playlist is then
seached in the playlist_dir and the ".m3u" extension is appended to the
name:
$ beet ls playlist:anotherplaylist
The configuration for the plugin looks like this:
playlist:
relative_to: library
playlist_dir: /path/to/playlists
The relative_to option specifies how relative paths in playlists are
handled. By default, paths are relative to the "library" directory. It
also possible to make them relative to the "playlist" or set the option
or set it to a fixed path.
