Improve staging query

 SELECT f.source_surl, f.job_id, f.file_id, j.copy_pin_lifetime, j.bring_online,
   j.user_dn, j.cred_id, j.source_space_token 
 FROM t_file f, t_job j 
 WHERE f.job_id = j.job_id 
   AND (j.BRING_ONLINE >= 0 OR j.COPY_PIN_LIFETIME >= 0) 
   AND f.start_time IS NULL AND f.file_state = 'STAGING'
   AND (f.hashed_id >= :hStart AND f.hashed_id <= :hEnd) 
   AND f.source_se = :source_se 
   AND j.user_dn = :user_dn 
   AND j.vo_name = :vo_name 
   AND f.vo_name = j.vo_name 
   AND f.job_finished IS NULL 
   AND NOT EXISTS ( 
       SELECT 
           1 FROM t_file f1 
       WHERE 
           f1.source_surl = f.source_surl AND f1.file_state='STARTED' 
           AND f1.vo_name = f.vo_name AND f1.job_finished IS NULL 
           AND f1.source_se = f.source_se
   ) 
  LIMIT :limit