Re: Query regarding function cleanup in extension upgrade path

Ayush Vatsa <ayushvatsa1810(at)gmail(dot)com> writes:
> To ask the question let me give a hypothetical example:-
> Suppose we have an extension named xyz with version 1.0. It has
> xyz--1.0.sql and xyz.c file. I have declared a function named fun() in the
> xyz--1.0.sql file and its definition in the xyz.c file.
> Now I want to drop this function in the next upgrade i.e. xyz--1.0--1.1 so
> I will use DROP FUNCTION fun(); in it and remove the definition from the
> xyz.c file.
> Here my doubt is wouldn't xyz--1.0 complain about the missing definition of
> fun() and if yes how can I clean up my function definition in the xyz.c
> file?

Yeah, you can't really remove the C extern symbol ever. You can
reduce the C function to a stub that just throws a not-supported
error, perhaps, but your users won't necessarily appreciate that.
It's usually better to make the shlib capable of supporting both
the 1.0 and 1.1 APIs, so that users aren't forced into updating
the extension's SQL declarations immediately.

If you look at the standard contrib modules, you'll find a number
of cases where there are backwards-compatibility functions that
just exist to support people who're still using an older version
of the extension's SQL declarations. Those are likely to remain
there indefinitely.

regards, tom lane