catalog query: performance of effective vs. effectiveRange

My colleague Christian Schneider achieved a massive performance 
improvement on a catalog query for an effective date range:
query['effective'] = {'query': datetime.now(), 'range': 'max'}
vs.
query['effectiveRange'] = datetime.now()
The latter is about 10 times faster on our live database (consisting of 
about 400k content objects, 50k of the queried content type).

I think this is not well-known, but then i may not be the most 
well-knowledgeable person around. Is this what Hanno talks about in this 
thread [2]?

And most important: Should we update the collective docs about querying 
by date? [2]

Kees

[1] http://plone.293351.n2.nabble.com/ZCatalog-vs-bad-indexes-td6251724.html

[2] 
http://collective-docs.readthedocs.org/en/latest/searching_and_indexing/query.html#querying-by-date

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