Django+Haystack+Whoosh,没有生产结果

我正在构建一个Django应用程序,使用Haystack+Whoosh进行搜索。在开发环境中,搜索按预期工作。但是,在生产中,搜索始终不返回结果。

发展:

$> python manage.py rebuild_index
...
All documents removed.
Indexing 8 categories
Indexing 4 documents

$> python manage.py shell
...
>>> from haystack.query import SearchQuerySet
>>> SearchQuerySet().all().count()
12

生产:

$> dokku run proj python manage.py rebuild_index -v2
...
All documents removed.
Skipping '<class 'django.contrib.admin.models.LogEntry'>' - no index.
...
Skipping '<class 'django.contrib.sessions.models.Session'>' - no index.
Indexing 7 categories
  indexed 1 - 7 of 7 (worker PID: 8).
Indexing 13 documents
  indexed 1 - 13 of 13 (worker PID: 8).
[INFO/MainProcess] process shutting down

$> dokku run proj python manage.py shell
...
>>> from haystack.query import SearchQuerySet
>>> SearchQuerySet().all().count()
0
>>> from django.conf import settings
>>> settings.HAYSTACK_CONNECTIONS['default']['PATH']
'/app/whoosh/index'

$> dokku run proj ls -la /app/whoosh
total 8
drwxr-xr-x  2 herokuishuser herokuishuser 4096 Nov 21 16:44 .
drwxr-xr-x 21 herokuishuser herokuishuser 4096 Nov 22 17:42 ..
-rw-r--r--  1 herokuishuser herokuishuser    0 Nov 21 16:43 .gitkeep

文件/设置:

# requirements.txt
Django==1.10.3
django-haystack==2.5.1
gunicorn==19.6.0
psycopg2==2.6.2
whitenoise==3.2.2
Whoosh==2.7.4
...

# runtime.txt
python-3.5.2

# proj/settings.py
...
HAYSTACK_CONNECTIONS = {
    'default': {
        'ENGINE': 'haystack.backends.whoosh_backend.WhooshEngine',
        'PATH': os.path.join(BASE_DIR, 'whoosh', 'index'),
    },
}
...

找到问题有什么指导吗?