Andreas Pflug <Andreas(dot)Pflug(at)web(dot)de> writes:
> There might be other cases of legal direct change of system catalog
> entries, e,g. varchar to text, if they all are only names for internally
> identical data structures. Can you tell which datatypes may be legally
> interchanged?
Right offhand I think text<->varchar and adjustment of length limits in
char, varchar, and perhaps numeric would be the only things useful
enough to worry about handling.
regards, tom lane