On Tue, Nov 4, 2025 at 5:00 PM Alexander Lakhin <[email protected]> wrote: > Please look at a new anomaly, introduced with 03d40e4b5: > CREATE TABLE t(i integer); > CREATE TABLE pt(i integer) PARTITION BY LIST(i); > > SET enable_seqscan = 'off'; > SELECT * FROM t UNION SELECT * FROM t > UNION ALL > SELECT * FROM pt; > produces: > ERROR: XX000: unrecognized node type: 0 > LOCATION: create_plan_recurse, createplan.c:538
I looked into this. The child relation with relid 3 (the scan on the partitioned table) is a dummy, so it is skipped in generate_union_paths(). As a result, the final setop relation ends up the same as the child relation with relid set to (1, 2). Then, generate_union_paths() creates an Append path using this relation's cheapest path as its subpath. Somehow, add_path() determines that this new Append path dominates the original cheapest path, causing the original cheapest path to be freed. This leads to the final Append path referencing a subpath that has already been freed. - Richard
