"Dave Lee" <davelee(dot)com(at)gmail(dot)com> writes:
> and I notice that there isn't any rows specified for converting
> varchar or text to int. Which raises the question, if I run:
> SELECT '123'::int;
> What conversion is actually happening here?
None. There is no type coercion there --- what that is really
specifying is invocation of the int data type's input function
on the given string.
I don't think your approach is going to work; you would have to
make your client programs emit things like
insert into mytab(integercol) values (''::varchar)
in order to get a runtime varchar-to-int cast to be applied.
At that point you might as well fix them properly.
regards, tom lane