BUG #16150: UPDATE set NULL value in non-null columns

From: PG Bug reporting form <noreply(at)postgresql(dot)org>
To: pgsql-bugs(at)lists(dot)postgresql(dot)org
Cc: maximaximax(at)gmail(dot)com
Subject: BUG #16150: UPDATE set NULL value in non-null columns
Date: 2019-12-05 09:17:34
Message-ID: 16150-dc6886080d71e985@postgresql.org
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The following bug has been logged on the website:

Bug reference: 16150
Logged by: Maxim Votyakov
Email address: maximaximax(at)gmail(dot)com
PostgreSQL version: 12.0
Operating system: Windows

Hi guys

Today I found a big problem, I can write a valid UPDATE which put NULL value
in non-null column.

Let's create a domain, two tables and insert 1 row into them:

create domain d_text_not_null as text default '' not null;

create table person (name d_text_not_null);
create table town (name d_text_not_null);

insert into person(name) values ('test');
insert into town(name) values ('test2');

select * from person; -- 1 row with value test

Now let's try to update person name to null. It failed and it is correct:

update person set name = null; -- SQL Error [23502]: ERROR: domain
d_text_not_null does not allow null values

But now let's try to update person name to with sub-query. It updates a row
without any problem:

update person set name = (select name from town where name = 'wrong'); -- 1
row updated

Let's check data and see the result:

select * from person; -- 1 row with value NULL in non-null column !!!

I think it is very dangerous and important bug and it has to be fixed to not
damage data in databases - if I backup/restore such tables they become


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