Guo Xiang Tan 5c230266d3
FIX: Inject extra lexemes for host lexeme.
```
discourse_development=# SELECT alias, lexemes FROM TS_DEBUG('www.discourse.org');
 alias |       lexemes
-------+---------------------
 host  | {www.discourse.org}

discourse_development=# SELECT TO_TSVECTOR('www.discourse.org');
      to_tsvector
-----------------------
 'www.discourse.org':1
```

Given the above lexeme, we will inject additional lexeme by splitting
the host on `.`. The actual tsvector stored will look something like

```
               tsvector
---------------------------------------
 'discourse':1 'discourse.org':1 'org':1 'www':1 'www.discourse.org':1
```
2020-07-14 15:32:40 +08:00
..