Re: MERGE issues around inheritance

On Sun, 25 May 2025 at 13:41, Dean Rasheed <dean.a.rasheed@gmail.com> wrote:
>
> On Sun, 25 May 2025 at 13:06, Tender Wang <tndrwang@gmail.com> wrote:
> >
> > For a partitioned table, we must pass rootResultRelInfo to ExecInsert(). I added the check before calling ExecInsert()
> > If it is a partitioned table, we continue to pass rootResultRelInfo. Otherwise, we pass resultRelInfo.
> > Please see the attached diff file. The patch passed all regression test cases.
> >
>
> No, I don't think that's the right fix. I'm looking at it now, and I
> think I have a fix, but it's more complicated than that. I'll post an
> update later.
>

The reason that MERGE must pass rootResultRelInfo to ExecInsert() for
a plain-inheritance table dates back to 387f9ed0a08. As that commit
demonstrates, it is possible for the parent to be excluded from the
plan, and so all of the entries in the resultRelInfo array may be for
different relations than rootResultRelInfo.

different relations than rootResultRelInfo."

I didn't fully understand the above sentence.  Can you give me more information or an example?

If the parent is excluded from the plan, the first entry in the resultRelInfo array will not be the parent but some surviving child.