Filter charmworld searches by score.

Filter charmworld searches by score.

This change introduces a new parameter to the API search called 'min_score'.
It defaults to a value of 1.0.  Searches will be filtered and only those
results with a score above min_score will be returned.

The min_score will not be used if the search is for all bundles or charms.

In addition, the number of results will be limited the smaller of 20 or the
limit provided.  Again, the limit is not applied if the search is for all
charms or bundles.

QA:

% bin/ingest --limit=20
% make run

In another window, interactively poke at it, e.g.

% http GET "http://127.0.0.1:2464/api/3/search?text=mysql&min_score=0"
% http GET "http://127.0.0.1:2464/api/3/search?text=mysql&min_score=2"
% http GET "http://127.0.0.1:2464/api/3/search?text=charmworld&min_score=0"

https://code.launchpad.net/~bac/charmworld/1287977/+merge/210660

(do not edit description out of merge proposal)

[bac, 2014-03-12 18:04:01]

Please take a look.

[benji, 2014-03-12 18:38:38]

LGTM

https://codereview.appspot.com/74900043/diff/1/charmworld/search.py
File charmworld/search.py (right):

https://codereview.appspot.com/74900043/diff/1/charmworld/search.py#newcode621
charmworld/search.py:621: hits = self._filter_by_score(hits, min_score)
A note explaining that we don't get scores for sorted queries might be nice
here.

https://codereview.appspot.com/74900043/diff/1/charmworld/tests/test_search.py
File charmworld/tests/test_search.py (right):

https://codereview.appspot.com/74900043/diff/1/charmworld/tests/test_search.p...
charmworld/tests/test_search.py:679: # Make more charms for a total of 22.
Some would say that this test should be broken into two discreet tests because
it does setup, assertions, more setup, more assertions.

https://codereview.appspot.com/74900043/diff/1/charmworld/tests/test_search.p...
charmworld/tests/test_search.py:710: # Make more charms for a total of 22.
Another candidate for two tests.

https://codereview.appspot.com/74900043/diff/1/charmworld/views/api/__init__.py
File charmworld/views/api/__init__.py (right):

https://codereview.appspot.com/74900043/diff/1/charmworld/views/api/__init__....
charmworld/views/api/__init__.py:723: min_score = float(min_score[0])
The min_score behavior is a little weird; maybe a description should be added to
the docstring.