Sphinx morphology stem_en not working

Question

I have a single-field Sphinx index with stemming set up as follows:

index main_sphinxalert
{
            # Options:
            type = rt
            path = /var/lib/sphinxsearch/data/main_sphinxalert
            morphology = stem_en

            # Fields:
            rt_field = query
}

I then insert:

mysql> INSERT INTO main_sphinxalert VALUES(201,'tables');
Query OK, 1 row affected (0.00 sec)

And select:

mysql> SELECT * FROM main_sphinxalert WHERE MATCH('tables');
+------+--------+
|  id  | weight |
+------+--------+
| 201  |  1709  |
+------+--------+
1 row in set (0.00 sec)

But can't select on a stem:

mysql> SELECT * FROM main_sphinxalert WHERE MATCH('table');
Empty set (0.00 sec)

Can anyone tell me what gives?

Answer 1

Turns out Sphinx will not read modifications to config files for a realtime index after it's been created: see here for info.

The way around this is to:

sudo service sphinxsearch stop

Then delete all index files (for me held in /var/lib/sphinxsearch/data/):

sudo rm main_sphinxalert.*

Then restart service:

sudo service sphinxsearch start

This means you lose your existing index, which will then have to be manually rebuilt from your database.