From: Tom Lane <tgl@sss.pgh.pa.us>
To: exclusion@gmail.com
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18634: Wrong varnullingrels with merge ... when not matched
 by source
In-reply-to: <18634-db5299c937877f2b@postgresql.org>
References: <18634-db5299c937877f2b@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Thu, 26 Sep 2024 18:00:01 -0000"
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Date: Thu, 26 Sep 2024 18:41:29 -0400
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PG Bug reporting form <noreply@postgresql.org> writes:
> The following script:
> CREATE TABLE t (a int);
> INSERT INTO t VALUES(1), (2);
> CREATE VIEW v AS SELECT a FROM t WHERE EXISTS (SELECT 1 FROM t);

> MERGE INTO v USING (SELECT * FROM generate_series(1,1)) AS s(a)
>   ON s.a = v.a WHEN NOT MATCHED BY SOURCE THEN DELETE;

> produces:
> ERROR:  XX000: wrong varnullingrels (b) (expected (b 4)) for Var 5/1
> LOCATION:  search_indexed_tlist_for_var, setrefs.c:2847

I haven't run this fully to ground, but what it looks like
is that preprocess_targetlist is generating row identity
Vars that lack required varnullingrels.  I don't understand
though why this only seems to affect MERGE.

			regards, tom lane