Kerem Kat <keremkat@gmail.com> writes:
> Union with NULL error persists without the corresponding patch. Here
> is the output from postgres without the patch:
> SELECT a FROM (SELECT 1 a) foo
> UNION
> SELECT a FROM (SELECT NULL a) foo2;
> ERROR: failed to find conversion function from unknown to integer
Yeah, this is a longstanding issue that is not simple to fix without
introducing other unpleasantnesses. It is not something you should
try to deal with at the same time as implementing CORRESPONDING.
regards, tom lane