conocer el tamaño de las bases de datos
select pg_database_size(pg_database.datname)) AS size FROM pg_database;
ver consultas en ejecucion
 select pg_class.relname, pg_locks.transactionid, pg_locks.mode, pg_locks.granted as "g",
   substr(pg_stat_activity.current_query,1,30), pg_stat_activity.query_start, 
   age(now(),pg_stat_activity.query_start) as "age", pg_stat_activity.procpid 
   from pg_stat_activity,pg_locks
   left outer join pg_class on 
   (pg_locks.relation = pg_class.oid)  
   where pg_locks.pid=pg_stat_activity.procpid 
   order by query_start;
 
