Incorrect result for IS NULL for row of nulls

[martint]

Per the SQL specification section 8.8 - null predicate:

<null predicate> ::=
  <row value predicand> <null predicate part 2>

1) Let R be the <row value predicand> and let V be the value of R.
2) ...
  b) ...
    i) The value of “R IS NULL” is
      1) If the value of every field of V is the null value, then True.

Currently, Trino incorrectly returns false:

trino> select (null, null) is null;

 _col0
-------
 false
(1 row)

[sahoss]

i'd like to explore a fix for this @martint. would that be ok?

[martint]

Yes, go for it!

[sahoss]

sharing my analysis. the incorrectness is due to a bug in the iterative optimizer rule SimplifyExpressions rewriter. adding this test case inside TestSimplifyExpressions is the way to reproduce this situation "closest" to the source of the bug.

 @Test
    public void testArrayNullPredicate() {
        assertSimplifies("(null, null) is NULL", "true");
    }

now, i am exploring how to fix it.