Xapian index not returning results

• Tested with the latest Haystack release
• Tested with the current Haystack master branch

Expected behaviour

I've recently upgraded a site from Django 1.3 to 1.8. I've had Xapian/Haystack search running flawlessly on this site until the upgrade. As a result of the Django upgrade, I was forced to also upgrade Haystack & Xapian-Haystack. The Xapian index is building (see xapian-check below), but isn't returning results. Whoosh works fine with this install, btw...but it's spelling suggestions leave much to be desired, so I really want to get Xapian working again.

$ ./manage.py rebuild_index
...
Indexing 282 products

Here's a look at xapian-check results. Looks ok to me:

$ xapian-check haystack
record:
baseB blocksize=8K items=282 lastblock=10 revision=1 levels=1 root=2
B-tree checked
okay record table structure checked OK

termlist:
baseB blocksize=8K items=564 lastblock=23 revision=1 levels=1 root=2
B-tree checked okay termlist table
structure checked OK

postlist:
baseB blocksize=8K items=8542 lastblock=77 revision=1 levels=1 root=2
B-tree checked okay postlist table
structure checked OK

position:
baseB blocksize=8K items=17532 lastblock=50 revision=1 levels=1 root=2
B-tree checked okay position table
structure checked OK

spelling:
baseB blocksize=8K items=4350 lastblock=16 revision=1 levels=1 root=2
B-tree checked okay spelling table:
Don't know how to check structure

synonym:
Lazily created, and not yet used.

No errors found

Actual behaviour

Getting 0 results from index:

>>> from haystack.query import SearchQuerySet
>>> sqs = SearchQuerySet().all()
>>> sqs.count()
0

Steps to reproduce the behaviour

1. Install all necessary requirements: Xapian, Xapian-Haystack, Django-Haystack, etc. (Re)build index. Test.

Configuration

I've tried this on 2 different systems with all sorts of versions and have encountered identical results.

OPERATING SYSTEM 1

• Operating system version: OSX 10.9.5
• Search engine version(s): Xapian 1.2.18-1.3.x
• Python version: 2.7.2
• Django version(s): 1.8.0-1.8.9
• Haystack version(s): 2.4.0-2.5.dev0

OPERATING SYSTEM 2

• Operating system version: CentOS 7.2/Cpanel
• Search engine version(s): Xapian 1.2.18-1.3.x
• Python version: 2.7.11 (virtualenv)
• Django version(s): 1.8.0-1.8.9
• Haystack version(s): 2.4.0-2.5.dev0

Start by reproducing the issue with the listed Django, Haystack, and Xapian versions, using the rebuild_index command and SearchQuerySet().all().count() shown in the report. Compare the failing Xapian backend with the working Whoosh setup and inspect the index/search configuration. Done means the rebuilt index returns the indexed products instead of zero results.