Re: unnesting multirange data types

On Sun, Jun 13, 2021 at 2:58 AM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> On Sun, Jun 13, 2021 at 1:16 AM Jonathan S. Katz <jkatz@postgresql.org> wrote:
> > On 6/12/21 5:57 PM, Alexander Korotkov wrote:
> > > On Sat, Jun 12, 2021 at 2:44 AM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> > >> ()On Sat, Jun 12, 2021 at 2:30 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > >>> On Fri, Jun 11, 2021 at 11:37:58PM +0300, Alexander Korotkov wrote:
> > >>>> On Fri, Jun 11, 2021 at 1:04 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > >>>>>
> > >>>>> +{ oid => '1293', descr => 'expand mutlirange to set of ranges',
> > >>>>>
> > >>>>> typo: mutlirange
> > >>>>
> > >>>> Fixed, thanks.
> > >>>>
> > >>>> The patch with the implementation of both unnest() and cast to array
> > >>>> is attached.  It contains both tests and docs.
> > >>>
> > >>> |+   The multirange could be explicitly cast to the array of corresponding
> > >>> should say: "can be cast to an array of corresponding.."
> > >>>
> > >>> |+ * Cast multirange to the array of ranges.
> > >>> I think should be: *an array of ranges
> > >>
> > >> Thank you for catching this.
> > >>
> > >>> Per sqlsmith, this is causing consistent crashes.
> > >>> I took one of its less appalling queries and simplified it to this:
> > >>>
> > >>> select
> > >>> pg_catalog.multirange_to_array(
> > >>>     cast(pg_catalog.int8multirange() as int8multirange)) as c2
> > >>> from (select 1)x;
> > >>
> > >> It seems that multirange_to_array() doesn't handle empty multiranges.
> > >> I'll post an updated version of the patch tomorrow.
> > >
> > > A revised patch is attached.  Now empty multiranges are handled
> > > properly (and it's covered by tests).  Typos are fixed as well.
> >
> > Tested both against my original cases using both SQL + PL/pgSQL. All
> > worked well. I also tested the empty multirange case as well.
> >
> > Overall the documentation seems to make sense, I'd suggest:
> >
> > +  <para>
> > +   The multirange can be cast to an array of corresponding ranges.
> > +  </para>
> >
> > becomes:
> >
> > +  <para>
> > +   A multirange can be cast to an array of ranges of the same type.
> > +  </para>
>
> Thank you. This change is incorporated in the attached revision of the patch.
>
> This thread gave me another lesson about English articles.  Hopefully,
> I would be able to make progress in future patches :)
>
> > Again, I'll defer to others on the code, but this seems to solve the use
> > case I presented. Thanks for the quick turnaround!
>
> Thank you for the feedback!

I've added the commit message to the patch.  I'm going to push it if
no objections.

------
Regards,
Alexander Korotkov