I just want to be sure and ask the list before I plunge into this.

I have a bunch of tables which I need to change a column type from
varchar(5) to varchar().
These tables are ~30millions deep and running the DDL on a NON-Slony
database takes ~2-4 hours (each table).

I want to know if I can do the DDL 

alter table foo alter type foo_column type character varying

individually on each slave/master table or I have to do it via slony via
EXECUTE script?