Re: SELECT for UPDATE and outer join?

I find the comments in initsplan.c as following.

/*
* Presently the executor cannot support FOR UPDATE/SHARE marking of
* rels appearing on the nullable side of an outer join. (It's
* somewhat unclear what that would mean, anyway: what should we
* mark when a result row is generated from no element of the
* nullable relation?) So, complain if target rel is FOR UPDATE/SHARE.
* It's sufficient to make this check once per rel, so do it only
* if rel wasn't already known nullable.
*/

IIRC, SQL:2003 also says the nullable side is not updatable, since it is not
key-preserved. See 7.12 <query specification> of ISO/IEC 9075-2:2003.
And I also got the idea from Oracle's SQL manual.

"Josh Berkus" <josh(at)agliodbs(dot)com> wrote
news:200508110843(dot)12819(dot)josh(at)agliodbs(dot)com(dot)(dot)(dot)
> Folks,
>
> ------------------------------
> SQL statement<select t0.po_number, t0.po_site_id, t0.po_supp_id,
> t1.pol_number,
> t1.pol_po_id, t1.pol_balance, t1.pol_qty, t1.pol_p_id, t1.pol_message,
> t1.pol_de
> ldate from s_purchase_order t0 left outer join s_purchase_orderline
> t1 on t0.
> po_number = t1.pol_po_id where t0.po_number = ? for update > with
> input values
> :java.lang.Integer:30239.
> Please examine the SQLException for more information.
> NestedException: java.sql.SQLException: ERROR: SELECT FOR UPDATE cannot
> be applied to the nullable side of an outer join
> -----------------------------
>
> So, my question is: why can't we apply FOR UPDATE to an outer join? Is
this
> defined in the SQL Spec?
>
> --
> Josh Berkus
> Aglio Database Solutions
> San Francisco
>
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