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
outerjoin. (It's  * somewhat unclear what that would mean, anyway: what should we  * mark when a result row is
generatedfrom no element of the  * nullable relation?) So, complain if target rel is FOR UPDATE/SHARE.  * It's
sufficientto 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@agliodbs.com> wrote
news:200508110843.12819.josh@agliodbs.com...
> 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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