From: PG Doc comments form <noreply@postgresql.org>
To: pgsql-docs@lists.postgresql.org
Cc: chalx.shop@gmail.com
Subject: New vs old values collision in UPDATE RETURNING docs
Date: Fri, 15 Feb 2019 16:16:21 +0000
Message-ID: <155024738129.22709.5993209813359536828@wrigleys.postgresql.org> (raw)
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/11/sql-update.html
Description:
What we have in doc:
<q>
[ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]
output_expression: An expression to be computed and returned by the UPDATE
command after each row is updated.
</q>
What we have in the wild (Pg8..11):
* when using field names, expression represents NEW values after update;
* when using sub-selects or joined table references, expression represents
OLD values before update.
POC code:
<code>
create temporary table test(id int primary key, status text not null);
insert into test(id, status) values(1, 'initial');
update test t set status='new'
where id=1
returning id,
status as new_status,
(select status from test where id=t.id) as old_status;
</code>
Thus that "after each row is updated" sentence is rather confusing.
/Alexey
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Subject: Re: New vs old values collision in UPDATE RETURNING docs
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