Hi,                             
                                
I've too much traffic to find an edge between locks.
I can hardly afford an application outage.
Using Slony 1.2.15, pg 8.2 and 8.3, having only one replication set.

My DDLs changes are usually pretty trivial (mostly "ADD COLUMN"): they
only touch one table at time, they they don't rename things, they never 
alter primary keys, they don't add triggers or rewrite rules.
All replicated tables have their own, explicit primary keys (no add key).
                                                         
Looking quickly at slony's source code, I thought this may be sufficient to
run my ALTERs on replicated tables, avoiding an heavyweight "EXECUTE SCRIPT":
                                                         
                                                         
  BEGIN;                                                 
  LOCK TABLE mytable;                                    
  -- Wait for pending events touching this table to propagate on subscribers.
  -- Then run the same "BEGIN ; LOCK TABLE mytable;" on all subscribers.

  -- On all nodes
  ALTER mytable ...

  -- On origin node (only there?)
  SELECT _mycluster.alterTableRestore(42);
  SELECT _mycluster.alterTableForReplication(42);

  -- On all nodes (origin and subscribers)
  COMMIT;


Would this work or did I overlooked something?

I wonder if the alterTableRestore and alterTableForReplication are mandatory
on subscribers, or only on origin. EXECUTE SCRIPT run them everywhere but
this doesn't look necessary when we're not touching triggers/rewrites (?).

And I'm not sure whether it would be wise to stop slon daemons meanwhile. My
understanding is that when avoiding ddlScript_complete(), aforementioned
actions wouldn't generate any event, so slon wouldn't notice anything.

Thanks