Re: BUG #18674: Partitioned table doesn't depend on access method it uses

On Sun, 27 Oct 2024 at 12:53, Kirill Reshke <reshkekirill@gmail.com> wrote:
>
> Hi!
>
> On Sat, 26 Oct 2024 at 19:27, PG Bug reporting form
> <noreply@postgresql.org> wrote:
> >
> > The following bug has been logged on the website:
> >
> > Bug reference:      18674
> > Logged by:          Alexander Lakhin
> > Email address:      exclusion@gmail.com
> > PostgreSQL version: 17.0
> > Operating system:   Ubuntu 22.04
> > Description:
> >
> > The following script:
> > CREATE ACCESS METHOD ham TYPE TABLE HANDLER heap_tableam_handler;
> > CREATE TABLE pt (a int) PARTITION BY LIST (a) USING ham;
> > DROP ACCESS METHOD ham;
> >
> > ends successfully, with the access method dropped, though then:
> > CREATE TABLE tp1 PARTITION OF pt FOR VALUES IN (1);
> >
> > fails with
> > ERROR:  cache lookup failed for access method 16385
> >
> > Whilst
> > CREATE TABLE t (a int) USING ham;
> > DROP ACCESS METHOD ham;
> >
> > fails with
> > ERROR:  cannot drop access method ham because other objects depend on it
> > DETAIL:  table t depends on access method ham
> > HINT:  Use DROP ... CASCADE to drop the dependent objects too.
> >
> > Reproduced starting from 374c7a229.
> >
>
> Nice catch!
>
> Did you dig into reasons? I did a little...
>
> After looking closely at the DefineRelation workflow, I discovered
> that it is  `RelationBuildLocalRelation` responsibility to add
> dependency between relation and its TAM. The bug arises from the fact
> that RELKIND_HAS_TABLE_AM doesn't respect partitioned relations.
> So, a trivial fix is attached.
>
> Does it look good for you?
>
> --
> Best regards,
> Kirill Reshke

As mentioned by Alexander off-list, v1 patch actually fails in a lot
of regression tests... My bad.

Seems that simply changing RELKIND_HAS_TABLE_AM marco is too invasive.
However, I will make another try. In v2 version, regression tests
still fail, i will adjust them, if patching this way is the right
approach to fix the problem..

script provided by Alexander:
CREATE ACCESS METHOD ham TYPE TABLE HANDLER heap_tableam_handler;
CREATE TABLE pt (a int) PARTITION BY LIST (a) USING ham;
DROP ACCESS METHOD ham;

now gives the correct output.


-- 
Best regards,
Kirill Reshke