Once the datastore is running its important to be able to sort the
results along the lines of various criteria. Lets create a sample
datastore.

First clean up from any other tests.
>>> import os
>>> assert os.system('rm -rf /tmp/test_ds/') == 0

>>> from olpc.datastore import DataStore
>>> from olpc.datastore import backingstore, model
>>> ds = DataStore()
>>> ds.registerBackend(backingstore.FileBackingStore)

>>> assert ds.mount("/tmp/test_ds")

>>> a = ds.create({'title':"Content A", 'author':"Bob", 'year:int':"1999", 'month':"Jan"}, '')
>>> b = ds.create({'title':"Content B", 'author':"Alice", 'year:int':"2000", 'month':"Jan"}, '')

Find should return both
>>> def find2uids(results): return [i['uid'] for i in results[0]]

>>> ds.complete_indexing()

>>> assert set(find2uids(ds.find())) == set([a,b])


But what if we want the results ordered?
>>> assert find2uids(ds.find(order_by=['title'])) == [a, b]
>>> assert find2uids(ds.find(order_by=['author'])) == [b, a]

By more than one key?

>>> assert find2uids(ds.find(order_by=['month', 'year'])) == [a, b]

and if we want to reverse order it?

>>> assert find2uids(ds.find(order_by=['-title'])) == [b, a]
>>> assert find2uids(ds.find(order_by=['-author'])) == [a, b]

>>> ds.stop()
>>> del ds
>>> assert os.system('rm -rf /tmp/test_ds/') == 0