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
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