Re: [HACKERS] Partition-wise aggregation/grouping

On Thu, Mar 8, 2018 at 9:15 AM, Jeevan Chalke
<jeevan.chalke@enterprisedb.com> wrote:
> I am not sure why we don't set reltarget into the grouped_rel too.
>
> But if we do so like we did in partially_grouped_rel, then it will be lot
> easier for partitionwise aggregate as then we don't have to pass target to
> functions creating paths like create_append_path. We now need to update
> generate_gather_paths() to take target too as it is now being called on
> grouped_rel in which reltarget is not set.
>
> But yes, if there is any specific reason we can't do so, then I think the
> same like Ashutosh Said. I didn't aware of such reason though.

I see no problem with setting reltarget for the grouped_rel.  Before
we added partially_grouped_rel, that rel computed paths with two
different targets: partial paths had the partial grouping target, and
non-partial paths had the ordinary grouping target.  But that's fixed
now.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company