sqlite_ext.FTSModel: MATCH'ing a single column
Correct, one needed to use the `match()` helper. I've added a method to `SearchField` as you suggested. Thanks for the quick fix!
SQLite FTS allows MATCH'ing a single column instead of the full table. An example from https://www.sqlite.org/fts3.html:

```sql
-- Example schema
CREATE VIRTUAL TABLE mail USING fts3(subject, body);

-- Example table population
INSERT INTO mail(docid, subject, body) VALUES(1, 'software feedback', 'found it too slow');
INSERT INTO mail(docid, subject, body) VALUES(2, 'software feedback', 'no feedback');
INSERT INTO mail(docid, subject, body) VALUES(3, 'slow lunch order',  'was a software problem');

-- Example queries
SELECT * FROM mail WHERE subject MATCH 'software';    -- Selects rows 1 and 2
SELECT * FROM mail WHERE body    MATCH 'feedback';    -- Selects row 2
SELECT * FROM mail WHERE mail    MATCH 'software';    -- Selects rows 1, 2 and 3
SELECT * FROM mail WHERE mail    MATCH 'slow';        -- Selects rows 1 and 3
```

Naturally (to me) one would want to write the column matching code like this:

```py
# SELECT * FROM mail WHERE subject MATCH 'software';
Mail.select().where(Mail.subject.match('software'))
```

However, this doesn't work, and instead it seems one has to write

```py
from playhouse.sqlite_ext import match

Mail.select().where(match(Mail.subject, 'software'))
```

and the `match` function isn't documented; only the `match` method of `FTSModel` is documented.

Maybe a `match` method could be added to `SearchField`?

Please excuse me if I missed anything obvious.