Database: academic
Question: return me the number of papers in PVLDB containing keyword " Keyword search " .
SQL:
SELECT COUNT ( DISTINCT t4.title ) FROM publication_keyword AS t2 JOIN keyword AS t1 ON t2.kid  =  t1.kid JOIN publication AS t4 ON t4.pid  =  t2.pid JOIN journal AS t3 ON t4.jid  =  t3.jid WHERE t3.name  =  "PVLDB" AND t1.keyword  =  "Keyword search";