This changes greatly improves the speed of `beet export` and `beet info`
when the `--include-keys` option is used. It also removes the globbing
feature of `--include-keys` that was added in #1295. (See #3762 for
discussion).
Listing all fields for an item requires querying the database to find
any flex attributes. This is slow when done for every item being
exported. We already have a way for the user to specify a fixed set
of keys, but we previously queried everything and filtered it afterwards.
The new approach is more efficient.
Code that iterates through all fields now have to handle invalid field
names. The export and info plugins output invalid fields as None.
Timings before:
> /usr/bin/time beet export -i title,path,artist -l Bob Dylan
13.26user 20.22system 0:34.01elapsed 98%CPU (0avgtext+0avgdata 52544maxresident)k
> /usr/bin/time beet export -l Bob Dylan
12.93user 20.15system 0:33.58elapsed 98%CPU (0avgtext+0avgdata 53632maxresident)k
Timings after:
> /usr/bin/time beet export -l Bob Dylan
13.33user 20.17system 0:34.02elapsed 98%CPU (0avgtext+0avgdata 53500maxresident)k
> /usr/bin/time beet export -i title,path,artist -l Bob Dylan
0.49user 0.07system 0:00.56elapsed 98%CPU (0avgtext+0avgdata 50496maxresident)k
Notice the dramatic speedup in the last example!
This was a vestige from when we used to need the unittest2 library for pre-2.7
compatibility. Now that we require Python 2.7, we aren't using that library
and this indirection wasn't doing any good.
This was breaking the `info` command in the click branch. I assume
that was because `run_command` was aliased to `run_with_output`.
It was also confusing in its own right, so I consider it a win
either way.
This reverts commit 9c41c39913.
That commit used byte strings for the `if __name__ == '__main__'` pattern,
which was necessary when we were doing unicode_literals. But it is wrong on
Python 3, and now that we're liberated from unicode_literals, we need to go
back to native strings for this comparison.
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.
