Andrew Gierth <andrew@tao11.riddles.org.uk> writes: > "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes: > Tom> Hmm. Maybe it'd be better if the default behavior in > Tom> expression_tree_walker/mutator did not include recursing into the > Tom> args, then?
> You'd think, but as I recall (I will re-check this to confirm) there > were more places where we _did_ need to recurse (especially during parse > analysis before we've matched up the sortgrouprefs), while most of the > places where recursion needed to be explicitly avoided already needed > special-case handling, so having the default the other way would likely > have required a special-case almost everywhere.
Fair enough. This is the kind of design choice that can be worth revisiting later; but if the conclusion is still the same, fine with me.
I think the culprit is that when replacing correlation uplevel vars with Params, we do not handle the SubLinks in the arguments of uplevel GroupingFunc. We expect build_subplan should take care of it. But in build_subplan, we ignore GroupingFunc incorrectly.
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c index 0881a208ac..e4918f275e 100644 --- a/src/backend/optimizer/plan/subselect.c +++ b/src/backend/optimizer/plan/subselect.c @@ -364,7 +364,8 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot, * SS_replace_correlation_vars). Do that now. */ if (IsA(arg, PlaceHolderVar) || - IsA(arg, Aggref)) + IsA(arg, Aggref) || + IsA(arg, GroupingFunc)) arg = SS_process_sublinks(root, arg, false);
I think we also need to change SS_process_sublinks to avoid recursing into the arguments of an outer GroupingFunc. And that leads to a fix as
