Re: ERROR: ORDER/GROUP BY expression not found in targetlist

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Jun 13, 2016 at 3:18 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>> In create_grouping_paths(), we are building partial_grouping_path and same
>> is used for gather path and other grouping paths (for partial paths).
>> However, we don't use it for partial path list and sort path due to which
>> path target for Sort path is different from what we have expected. Is there
>> a problem in applying partial_grouping_path for partial pathlist?
>> Attached patch just does that and I don't see error with patch.

> It doesn't seem like a good idea to destructive modify
> input_rel->partial_pathlist. Applying the projection to each path
> before using it would probably be better.

I think the real question here is why the code removed by 04ae11f62
was wrong. It was unsafe to use apply_projection_to_path, certainly,
but using create_projection_path directly would have avoided the
stated problem. And it's very unclear that this new patch doesn't
bring back that bug in a different place.

I am not very happy that neither 04ae11f62 nor this patch include
any regression test case proving that a problem existed and has
been fixed.

regards, tom lane