Re: Is a UDF binary portable across different minor releases and PostgreSQL distributions?

> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> writes:
> > Option 2:
> > Rebuild UDFs with the target PostgreSQL distribution.
> > You do not have to rebuild UDFs when you upgrade or downgrade the
> > minor release. (If your UDF doesn't work after changing the minor
> > release, it's the bug of PostgreSQL. You can report it to
> > pgsql-bugs.)
>
> I do not like either of those. We try hard not to break extensions in minor
> releases, but I'm not willing to state it as a hard-and-fast policy that
> we never will --- especially because there's no bright line as to which
> internal APIs extensions can rely on or not. With sufficiently negative
> assumptions about what third-party authors might have chosen to do, it could
> become impossible to fix anything at all in released branches.

I feel empathy, but I think something needs to be documented for users to upgrade and/or change distributions with relief. In practice, though it may be a shame, isn't option 1 the current answer?

Again, the current situation seems similar to the Linux loadable kernel modules. So PostgreSQL is not alone. See "Binary compatibility" section in:

https://en.wikipedia.org/wiki/Loadable_kernel_module

> In practice, extensions seldom need to be modified for new minor releases.
> But there's a long way between that statement and a promise that it won't
> ever happen for any conceivable extension.

I think so, too.

> To make this situation better, what we'd really need is a bunch of work
> to identify and document the specific APIs that we would promise won't change
> within a release branch. That idea has been batted around before, but
> nobody's stepped up to do all the tedious (and, no doubt, contentious) work
> that would be involved.

I can't yet imagine if such API (including data structures) can really be defined so that UDF developers feel comfortable with its flexibility. I wonder how other OSes provide such API and ABI.

Regards
Takayuki Tsunakawa