Fix unboundedness opt

Author: Dandandan

datafusion/core/tests/physical_optimizer/sanity_checker.rs

@@ -147,7 +147,7 @@ impl QueryCase {
                 error.as_str()
             );
         } else {
-            assert!(plan.is_ok())
+            assert!(plan.is_ok(), "plan: {:?} should be ok", plan);
         }
         Ok(())
     }

datafusion/physical-optimizer/src/join_selection.rs

@@ -571,7 +571,8 @@ pub(crate) fn swap_join_according_to_unboundedness(
             hash_join.swap_inputs(PartitionMode::CollectLeft)
         }
         (PartitionMode::Auto, _) => {
-            internal_err!("Auto is not acceptable for unbounded input here.")
+            // Default to Partitioned mode, so it won't be swapped again
+            hash_join.swap_inputs(PartitionMode::Partitioned)
         }
     }
 }