Re: [PG19] Wrong results from NOT NULL-based expression simplification

[Fujii Masao]

On Sat, Oct 10, 2026 at 9:53 AM Richard Guo <guofengli...@gmail.com> wrote:
> The fix covers all three, but I only back-patched it to v19, since
> there are no field reports and it changes the typmod exposed by a
> reduced CASE expression.

Codex reported that commit d8ce0050a6c causes the following INSERT to fail,
and I confirmed it. Is this a bug?

---------------------------------
CREATE TABLE t (a varchar(20) NOT NULL, b varchar(20));
CREATE UNIQUE INDEX t_idx ON t ((COALESCE(NULL::varchar, a, b)));

INSERT INTO t VALUES ('x', 'y')
ON CONFLICT ((COALESCE(NULL::varchar, a, b))) DO NOTHING;

ERROR:  there is no unique or exclusion constraint matching the ON
CONFLICT specification
---------------------------------

Regards,

-- 
Fujii Masao