On Mon, Jun 13, 2016 at 7:51 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > Robert Haas <robertmh...@gmail.com> writes: > > On Mon, Jun 13, 2016 at 3:18 AM, Amit Kapila <amit.kapil...@gmail.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. >
This new patch still doesn't seem to be right, but it won't bring back the original problem because apply_projection_to_path will be only done if grouped_rel is parallel_safe which means it doesn't have any parallel-unsafe or parallel-restricted clause in quals or target list. > 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. > It is slightly tricky to write a reproducible parallel-query test, but point taken and I think we should try to have a test unless such a test is really time consuming. With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
