Re: BUG #18526: 'UPDATE' inconsistency using index scan with 'NOT EXIST' after upgrading to PostgreSQL 16

PG Bug reporting form <noreply@postgresql.org> writes:
> Expected Result: All records that meet the criteria should be updated
> regardless of using index scan or seq scan.
> Actual Result: When PostgreSQL 16 uses index scan, it fails to find and
> update all records. By changing random_page_cost to a value that forces the
> use of seq scan, all records are updated correctly.

I see that the problematic plan involves a Merge Right Anti Join step,
which makes me guess that this is the same bug recently reported in

https://www.postgresql.org/message-id/flat/18522-c7a8956126afdfd0%40postgresql.org

Are you in a position to try the patch posted in that thread?

            regards, tom lane