From: Tom Lane <tgl@sss.pgh.pa.us>
To: postgresql@middaysomewhere.com
cc: Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17558: 15beta2: Endless loop with UNIQUE NULLS NOT DISTINCT
 and INSERT ... ON CONFLICT
In-reply-to: <17558-3f6599ffcf52fd4a@postgresql.org>
References: <17558-3f6599ffcf52fd4a@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Mon, 25 Jul 2022 01:04:06 -0000"
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Date: Mon, 25 Jul 2022 11:39:40 -0400
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PG Bug reporting form <noreply@postgresql.org> writes:
> In PostgreSQL 15 beta, when I try to insert a NULL value which violates a
> "UNIQUE NULLS NOT DISTINCT" constraint, PostgreSQL will get stuck in an
> endless loop if the command includes an "ON CONFLICT" clause. 

> CREATE TABLE test (val TEXT UNIQUE NULLS NOT DISTINCT);
> INSERT INTO test (val) VALUES ('a') ON CONFLICT DO NOTHING; -- inserts 'a'
> INSERT INTO test (val) VALUES ('a') ON CONFLICT DO NOTHING; -- does
> nothing
> INSERT INTO test (val) VALUES (NULL) ON CONFLICT DO NOTHING; -- inserts
> NULL
> INSERT INTO test (val) VALUES (NULL) ON CONFLICT DO NOTHING; --
> unresponsive

Yup, still a problem in HEAD.  It correctly reports an error if
you just "INSERT INTO test (val) VALUES (NULL)", but something
in the ON CONFLICT code path seems not to be on board with this.
Peter?

			regards, tom lane