Postgres: Blocking Lock Wait Events

 select
    round(EXTRACT(EPOCH FROM (clock_timestamp() - query_start))::numeric, 5) as query_age ,  
    round(EXTRACT(EPOCH FROM (clock_timestamp() -  xact_start))::numeric, 5) as xact_age,
    pid, 
    pg_blocking_pids(PID), 
    wait_event, 
    substr(query , 1, 80)
    query ,
    * 
    --,  pg_terminate_backend(PID)
from pg_stat_activity a,
        (select  unnest( string_to_array(replace(replace(pg_blocking_pids(PID)::text,'{',''),'}',''), ','))  as bpids, 
                 lower(query)   
         from pg_stat_activity
         --where lower(query) like '%drop%' or lower(query) like  '%alter%' 
        ) b
where 
  PID = b.bpids::integer ;