return me the paper in PVLDB with the most citations .
SELECT t2.title FROM publication AS t2 JOIN journal AS t1 ON t2.jid  =  t1.jid WHERE t1.name  =  "PVLDB" ORDER BY t2.citation_num DESC LIMIT 1;
SELECT t2.title FROM publication AS t2 JOIN journal AS t1 ON t2.jid  =  t1.jid WHERE t1.name  =  "PVLDB" ORDER BY t2.citation_num DESC LIMIT 1;
[{'Nenhum': 'Nenhum resultado encontrado'}]