[BUG] ON CONFLICT DO UPDATE SET x = EXCLUDED. errors or silently writes NULL - Mailing list pgsql-hackers

Repro:

-- plan table

    DROP TABLE IF EXISTS t;
    CREATE TABLE t (id int PRIMARY KEY,
                    a  int,
                    c  int GENERATED ALWAYS AS (a * 10) VIRTUAL);
    INSERT INTO t VALUES (1, 5);

    INSERT INTO t VALUES (1, 7)
        ON CONFLICT (id) DO UPDATE SET a = EXCLUDED.c;
    -- ERROR:  unexpected virtual generated column reference
   

-- Partitioned table: 

    DROP TABLE IF EXISTS tp;
    CREATE TABLE tp (id int PRIMARY KEY,
                     a  int,
                     c  int GENERATED ALWAYS AS (a * 10) VIRTUAL)
        PARTITION BY RANGE (id);
    CREATE TABLE tp1 PARTITION OF tp FOR VALUES FROM (1) TO (100);
    INSERT INTO tp VALUES (1, 5);

    INSERT INTO tp VALUES (1, 7)
        ON CONFLICT (id) DO UPDATE SET a = EXCLUDED.c;

    SELECT * FROM tp

 id | a | c
----+---+---
  1 |   |  


We have two options to fix, (1) throw an error for partitioned tables similar to plain tables or

(2) support the scenario fixing for both the cases.

I tried fixing this by replacing build_tlist_index with build_tlist_index_other_vars . This fix

works because build_tlist_index_other_vars only indexes plain-Var TEs of exclRelTlist and 

leaves has_non_vars = false, so fix_join_expr skips whole-subtree matching and never collapses

 the VGC-expanded (EXCLUDED.a * 10) in onConflictSet back into a Var(INNER_VAR, vgc_attno).

I am not super familiar with this area so I am not sure if this breaks anything. Ran the existing 

tests and they seem to be passing.

Thanks,
Satya