Compare NULL types (apache#5158)

Author: melgenek

datafusion/core/tests/sqllogictests/test_files/pg_compat/pg_compat_type_coercion.slt

@@ -95,20 +95,17 @@ select pg_typeof(false or true), pg_typeof(true or false);
 bool bool
 
 
-# TODO: run for DataFusion as well after #4335
-onlyif postgres
 query ??
 select null and null, null or null;
 ----
 NULL NULL
 
 
-# TODO: uncomment after #4335
-#onlyif DataFusion
-#query ??
-#select arrow_typeof(null and null), arrow_typeof(null or null);
-#----
-#Boolean Boolean
+onlyif DataFusion
+query ??
+select arrow_typeof(null and null), arrow_typeof(null or null);
+----
+Boolean Boolean
 
 
 onlyif postgres

datafusion/expr/src/type_coercion/binary.rs

@@ -100,7 +100,7 @@ pub fn coerce_types(
         Operator::And | Operator::Or => match (lhs_type, rhs_type) {
             // logical binary boolean operators can only be evaluated in bools or nulls
             (DataType::Boolean, DataType::Boolean) => Some(DataType::Boolean),
-            (DataType::Null, DataType::Null) => Some(DataType::Null),
+            (DataType::Null, DataType::Null) => Some(DataType::Boolean),
             (DataType::Boolean, DataType::Null) | (DataType::Null, DataType::Boolean) => {
                 Some(DataType::Boolean)
             }
@@ -1144,13 +1144,13 @@ mod tests {
             DataType::Null,
             DataType::Null,
             Operator::Or,
-            DataType::Null
+            DataType::Boolean
         );
         test_coercion_binary_rule!(
             DataType::Null,
             DataType::Null,
             Operator::And,
-            DataType::Null
+            DataType::Boolean
         );
         test_coercion_binary_rule!(
             DataType::Null,