Re: Segfault in RI UPDATE CASCADE on partitioned tables with LIKE+ATTACH child (attnum drift)

On Fri, 17 Oct 2025 at 14:21, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> Thanks for the detailed report. It seems to have been caused by
> ba9a7e3921. For some reason the ResultRelInfo.ri_RootResultRelInfo
> isn't set for this partition which causes ExecGetChildToRootMap() to
> think no translation is required.

The problem is with the ResultRelInfo caching that's in
ExecGetTriggerResultRel(). The code there tries looking into the
estate's es_opened_result_relations, es_tuple_routing_result_relations
and es_trig_target_relations Lists to see if the ResultRelInfo was
created before. In the problem case the ResultRelInfo is found in
es_trig_target_relations and unfortunately it's been set up by some
code in afterTriggerInvokeEvents() which passes a NULL rootRelInfo.
This means when ExecGetTriggerResultRel() is called again this time
passing the correct rootRelInfo, the cached one that has the NULL
ri_RootResultRelInfo is found and returned.

This results in the ExecGetChildToRootMap() code doing the wrong thing
because it sees a NULL ri_RootResultRelInfo therefore does not
translate the slot into the slow format of the partitioned table.

I've attached a patch which fixes the problem. I'm just not sure if
it's the right fix for the problem. I suspect the real problem is down
to the fact that ExecGetTriggerResultRel() passes a NULL rootRelInfo
in the first place. I just don't see a good way to figure out what the
parent table should be so we know to create a parent ResultRelInfo as
the trigger that is firing is for the partition, not the partitioned
table. I don't see any way to figure out that the trigger is being
fired because it's cascading an update of its parent partitioned
table... At a guess, it feels like there might be some fields missing
in AfterTriggerShared to figure this out.

Any thoughts on this Amit?

David