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

> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
> "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.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
"Binarycompatibility" 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
comfortablewith its flexibility.  I wonder how other OSes provide such API and ABI.
 

Regards
Takayuki Tsunakawa