Re: pg_dump is broken for partition tablespaces

On 2019-03-07 15:25:34 +1300, David Rowley wrote:
> On Thu, 7 Mar 2019 at 11:37, Andres Freund <andres(at)anarazel(dot)de> wrote:
> >
> > On 2019-03-07 11:31:15 +1300, David Rowley wrote:
> > > Do you think it's fine to reword the docs to make this point more
> > > clear, or do you see this as a fundamental problem with the patch?
> >
> > Hm, both? I mean I wouldn't necessarily characterize it as "fundamental"
> > problem, but ...
>
> Okay, so if I understand you correctly, you're complaining about the
> fact that if the user does:
>
> CREATE TABLE p (a int) PARTITION BY LIST(a) TABLESPACE pg_default;
>
> that the user intended that all future partitions go to pg_default and
> not whatever default_tablespace is set to at the time?

Correct. And also, conversely, if default_tablespace was set to frakbar
at the time of CREATE TABLE, but no explicit TABLESPACE was provided,
that that should *not* be the default for new partitions; rather
default_tablespace should be consulted again.

> If I understand what you're saying correctly, then the listp1_a_idx
> should have been created in pg_default since that's what the default
> partitioned index tablespace was set to.

That's how I understand the intent of the user yes.

> > I don't think the argument that the user intended to explicitly set a
> > tablespace holds much water if it was just set via default_tablespace,
> > rather than an explicit TABLESPACE. I think iff you really want
> > something like this feature, you'd have to mark a partition's
> > reltablespace as 0 unless an *explicit* assignment of the tablespace
> > happened. In which case you also would need to explicitly emit a
> > TABLESPACE for the partitioned table in pg_dump, to restore that.
>
> I think emitting an explicit tablespace in pg_dump for partitioned
> tables (when non-zero) might have issues for pg_restore's
> --no-tablespaces option.

Yea, there'd probably need to be handling in pg_backup_archiver.c or
such, not sure how to do that best.

Greetings,

Andres Freund