fix: set null_equals_null to false when convert_cross_join_to_inner_join (#11738)

Author: jonahgao

datafusion/optimizer/src/push_down_filter.rs

@@ -1127,7 +1127,7 @@ fn convert_cross_join_to_inner_join(cross_join: CrossJoin) -> Result<Join> {
         on: vec![],
         filter: None,
         schema: DFSchemaRef::new(join_schema),
-        null_equals_null: true,
+        null_equals_null: false,
     })
 }
 

datafusion/sqllogictest/test_files/join.slt

@@ -1108,4 +1108,26 @@ statement ok
 DROP TABLE t0;
 
 statement ok
-DROP TABLE t1;
+DROP TABLE t1;
+
+# Test SQLancer issue: https://github.com/apache/datafusion/issues/11704
+query II
+WITH
+    t1 AS (SELECT NULL::int AS a),
+    t2 AS (SELECT NULL::int AS a)
+SELECT * FROM
+  (SELECT * FROM t1 CROSS JOIN t2)
+WHERE t1.a == t2.a
+  AND t1.a + t2.a IS NULL;
+----
+
+# Similar to above test case, but without the equality predicate
+query II
+WITH
+    t1 AS (SELECT NULL::int AS a),
+    t2 AS (SELECT NULL::int AS a)
+SELECT * FROM
+  (SELECT * FROM t1 CROSS JOIN t2)
+WHERE t1.a + t2.a IS NULL;
+----
+NULL NULL