On 2019/04/17 12:58, David Rowley wrote: > On Wed, 17 Apr 2019 at 15:54, Tom Lane <t...@sss.pgh.pa.us> wrote: >> >> Amit Langote <langote_amit...@lab.ntt.co.jp> writes: >>> On 2019/04/17 11:29, David Rowley wrote: >>>> Where do you think the output list for EXPLAIN VERBOSE should put the >>>> output column list in this case? On the Append node, or just not show >>>> them? >> >>> Maybe, not show them? >> >> Yeah, I think that seems like a reasonable idea. If we show the tlist >> for Append in this case, when we never do otherwise, that will be >> confusing, and it could easily break plan-reading apps like depesz.com. >> >> What I'm more worried about is whether this breaks any internal behavior >> of explain.c, as the comment David quoted upthread seems to think. >> If we need to have a tlist to reference, can we make that code look >> to the pre-pruning plan tree, rather than the planstate tree? > > I think most of the complexity is in what to do in > set_deparse_planstate() given that there might be no outer plan to > choose from for Append and MergeAppend. This controls what's done in > resolve_special_varno() as this descends the plan tree down the outer > side until it gets to the node that the outer var came from. > > We wouldn't need to do this if we just didn't show the targetlist in > EXPLAIN VERBOSE, but there's also MergeAppend sort keys to worry about > too. Should we just skip on those as well?
I guess so, if only to be consistent with Append. Thanks, Amit
