On Sun, Jan 28, 2018 at 10:13 PM, Amit Kapila <amit.kapil...@gmail.com> wrote: > If we want to get rid of Gather (Merge) checks in > apply_projection_to_path(), then we need some way to add a projection > path to the subpath of gather node even if that is capable of > projection as we do now. I think changing the order of applying > scan/join target won't address that unless we decide to do it for > every partial path. Another way could be that we handle that in > generate_gather_paths, but I think that won't be the idle place to add > projection. > > If we want, we can compute the parallel-safety of scan/join target > once in grouping_planner and then pass it in apply_projection_to_path > to address your main concern.
I spent some time today hacking on this; see attached. It needs more work, but you can see what I have in mind. It's not quite the same as what I outlined before because that turned out to not quite work, but it does remove most of the logic from apply_projection_to_path(). -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
parallel-paths-tlist-cost-rmh.patch
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