Truncate table hanging with no other running queries

Question

Maybe once every other month I get a truncate table command that just hangs and dies.  Never on the same table, and when I check for other running queries there are none except the truncate (select * from stv_recents where status<>'Done').  I need to reboot the server to get it to run.  How can I identify what is actually locking the table?

Accepted Answer

Here's a few stock queries I use to investigate  
  
select t.relname,pid,mode,granted   
from pg_locks l, pg_stat_all_tables t   
where l.relation=t.relid order by relation asc;  
  
select distinct(relation) table_id  
,xid  
,pid  
,txn_start  
,lock_mode  
,trim(nspname)   schema_name  
,trim(relname)   table_name  
from svv_transactions  
left join pg_class on pg_class.oid = svv_transactions.relation  
join pg_namespace on pg_namespace.oid = relnamespace;  
  
You can also use stv_locks;

Truncate table hanging with no other running queries

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