Include import of __future__ features division, absolute_imports and
print_function everywhere. Don't add unicode_literals yet for it is
harder to convert.
Goal is smoothing the transition to python 3.
In preparation for enabling queries over flexattrs, this is a new path that
lets queries avoid generating SQLite expressions altogether. Any query that
can be completely evaluated in SQLite will be, but when it can't, we now fall
back to running the entire query in Python by selecting everything from the
database and running the `match` predicate.
To begin with, this mechanism replaces RegisteredFieldQueries, which
previously used Python callbacks for evaluation. Now they just indicate that
they're slow queries and the query system falls back automatically.
This has the great upside that it lets use implement arbitrarily complex
queries without shoehorning everything into SQLite when that (a) is way too
complicated and (b) doesn't buy us much performance anyway. The obvious
drawback is that any code dealing with queries now has to handle two cases
(slow and fast).
In the future, we could optimize this further by combing fast and slow query
styles. For example, if you want to match with a substring *and* a regular
expression, we can do a first pass in SQLite and apply the regex predicate on
the results. Avoided for now because premature optimization, etc., etc.
Next step: implement flexattr matches as slow queries.
The initial idea for this refactor was motivated by the need to make
PluginQuery.match() have the same method signature as the match() methods on
other queries. That is, it needed to take an *item*, not the pattern and
value. (The pattern is supplied when the query is constructed.) So it made
sense to move the value-to-pattern code to a class method.
But then I realized that all the other FieldQuery subclasses needed to do
essentially the same thing. So I eliminated PluginQuery altogether and
refactored FieldQuery to subsume its functionality. I then changed all the
other FieldQuery subclasses to conform to the same pattern.
This has the side effect of allowing different kinds of queries (even
non-field queries) down the road.
Renamed fuzzy_search to fuzzy and rdm to random. These names should be easier
to remember since they are the same as the commands they provide.
--HG--
rename : beetsplug/fuzzy_search.py => beetsplug/fuzzy.py
rename : beetsplug/rdm.py => beetsplug/random.py
rename : docs/plugins/fuzzy_search.rst => docs/plugins/fuzzy.rst
rename : docs/plugins/rdm.rst => docs/plugins/random.rst
