Re: Row IS NULL question

> I wrote:
> > Moving makeRowNullTest() doesn't seem like a big deal, but changing
> > ExecEvalNullTest would take some added code. Do we want to tackle that
> > during beta, or hold off till 8.3? An argument for doing it now is that
> > we just added nulls-in-arrays in 8.2, and it'd be good if the semantics
> > of that were right the first time rather than changing later.
>
> Now that I look more closely, makeRowNullTest() is actually WRONG even
> for the cases it handles. SQL99/SQL2003 define <null predicate> thus:
>
> 1) Let R be the value of the <row value expression>.
>
> 2) If every value in R is the null value, then "R IS NULL" is true;
> otherwise, it is false.
>
> 3) If no value in R is the null value, then "R IS NOT NULL" is
> true; otherwise, it is false.
>
> makeRowNullTest() is set up to return TRUE for an IS NOT NULL test if
> *any* element of R is non null:
>
> regression=# explain select * from int8_tbl x where row(x.q1,x.q2) is not null;
>
> QUERY PLAN
> -----------------------------------------------------------
> Seq Scan on int8_tbl x (cost=0.00..1.05 rows=5 width=16)
> Filter: ((q1 IS NOT NULL) OR (q2 IS NOT NULL))
> (2 rows)
>
> So this is clearly a bug and clearly one of long standing --- we've been
> getting this wrong since PG 7.3 :-(
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>

Would it be correct to do the null test in ExecEvalNullTest

(I would like to learn what happens but somehow I just cannot get the
debugger on makeRowNullTest in gram.c)

On Thu, 2006-09-28 at 14:38 -0400, Tom Lane wrote:

--
Regards,
Gevik Babakhani
http://www.postgresql.nl
http://www.truesoftware.nl