Amit Kapila <amit.kap...@enterprisedb.com> writes: > On Mon, Jun 13, 2016 at 7:51 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> 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. The problem cited in 04ae11f62's commit message is that apply_projection_to_path would overwrite the paths' pathtargets in-place, causing problems if they'd been used for other purposes elsewhere. I do not share your confidence that using apply_projection_to_path within create_grouping_paths is free of such a hazard. regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers