ORDER BY changes result size when combined with DISTINCT

[niklas88]

This was found by Tobias Matysiak: For queries with multiple columns adding an ORDER BY clause can change the result set.

See for example the following query with and without ORDER BY

PREFIX fb: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?cityname ?popcount WHERE {
    ?city fb:type.object.type fb:location.citytown .
    ?city fb:type.object.name ?cityname .
    ?city fb:location.location.containedby ?country .
    ?city fb:location.statistical_region.population ?population .
    ?population fb:measurement_unit.dated_integer.number ?popcount .
}
ORDER BY DESC(?popcount)
LIMIT 100

My guess is that DISTINCT needs to sort by all columns combined before any ORDER BY sorting if it should give really distinct results. Will have to check with the standards documents if this is actually what DISTINCT does. @Buchhold any quick knowledge?

[niklas88]

This was fixed in #133 and I just confirmed it now works as expected