Re: posgres 12 bug (partitioned table)

On Thu, Jun 4, 2020 at 12:57 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Pavel Biryukov <79166341370@yandex.ru> writes:
> > Hello. I'm catch error "virtual tuple table slot does not have system
> > attributes" when inserting row into partitioned table with RETURNING
> > xmin
>
> Reproduced here.  The example works in v11, and in v10 if you remove
> the unnecessary-to-the-example primary key, so it seems like a clear
> regression.  I didn't dig for the cause but I suppose it's related
> to Andres' slot-related changes.

I wonder whether it's really correct to classify this as a bug. The
subsequent discussion essentially boils down to this: the partitioned
table's children could use any AM, and they might not all use the same
AM. The system columns that are relevant for the heap may therefore be
relevant to all, some, or none of the children. In fact, any fixed
kind of tuple table slot we might choose to use for the parent has
this problem. If all of the children are of the same type -- and today
that would have to be heap -- then using that type of tuple table slot
for the parent as well would make sense. But there's no real reason
why that's the correct answer in general. If the children are all of
some other type, using a heap slot for the parent is wrong; and if
they're all of different types, it's unclear that anything other than
a virtual slot makes any sense.

-- 
Robert Haas
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