RE: Ability to reference other extensions by schema in extension scripts

> On Sun, Feb 26, 2023 at 01:39:24AM -0500, Regina Obe wrote:
> 
> > > 1) Just don't allow any extensions referenced by other
> > >    extensions to be relocatable.
> >
> > Attached is my revision 3 patch, which follows the proposed #1.
> > Don't allow schema relocation of an extension if another extension
> > requires it.
> 
> I've built a version of PostgreSQL with this patch applied and I confirm
it
> works as expected.
> 
> The "ext1" is relocatable and creates a function ext1log():
> 
>   =# create extension ext1 schema n1;
>   CREATE EXTENSION
> 
> The "ext2" is relocatable and creates a function ext2log() relying on the
> ext1log() function from "ext1" extension, referencing it via
> @extschema:ext1@:
> 
>   =# create extension ext2 schema n2;
>   CREATE EXTENSION
>   =# select n2.ext2log('hello'); -- things work here
>   ext1: ext2: hello
> 
> By creating "ext2", "ext1" becomes effectively non-relocatable:
> 
>   =# alter extension ext1 set schema n2;
>   ERROR:  cannot SET SCHEMA of extension ext1 because other extensions
>   require it
>   DETAIL:  extension ext2 requires extension ext1
> 
> Drop "ext2" makes "ext1" relocatable again:
> 
>   =# drop extension ext2;
>   DROP EXTENSION
>   =# alter extension ext1 set schema n2;
>   ALTER EXTENSION
> 
> Upon re-creating "ext2" the referenced ext1 schema will be the correct
one:
> 
>   =# create extension ext2 schema n1;
>   CREATE EXTENSION
>   =# select n1.ext2log('hello');
>   ext1: ext2: hello
> 
> The code itself builds w/out warnings with:
> 
>   mkdir build
>   cd build
>   ../configure
>   make 2> ERR # ERR is empty
> 
> The testsuite reports all successes:
> 
>   make check
>   [...]
>   =======================
>    All 213 tests passed.
>   =======================
> 
> Since I didn't see the tests for extension in there, I've also explicitly
run that
> portion:
> 
>   make -C src/test/modules/test_extensions/ check
>   [...]
>   test test_extensions              ... ok           32 ms
>   test test_extdepend               ... ok           12 ms
>   [...]
>   =====================
>    All 2 tests passed.
>   =====================
> 
> 
> As mentioned already the downside of this patch is that it would not be
> possibile to change the schema of an otherwise relocatable extension once
> other extension depend on it, but I can't think of any good reason to
allow
> that, as it would mean dependent code would need to always dynamically
> determine the install location of the objects in that extension, which
sounds
> dangerous, security wise.
> 
> --strk;
> 
>   Libre GIS consultant/developer
>   https://strk.kbt.io/services.html

Oops I had forgotten to submit the updated patch strk was testing against in
my fork.
He had asked me to clean up the warnings off list and the description.

Attached is the revised.
Thanks strk for the patient help and guidance.

Thanks,
Regina