refactor: Simplify the partial full handling for distinct aggregation (…

…facebookincubator#11876)

Summary:

We should have the case in aggregation add input that the partial aggregation has been marked as full
but there is no new distinct detected for a distinct aggregation operator. Instead of clearing the partial
full flag, we should add a distinct check there instead for simplicity.

Differential Revision: D67288365

velox/exec/HashAggregation.cpp

@@ -206,10 +206,9 @@ void HashAggregation::addInput(RowVectorPtr input) {
       // Save input to use for output in getOutput().
       input_ = input;
     } else {
-      // If no new distinct groups (meaning we don't have anything to output),
-      // then we need to ensure we 'need input'. For that we need to reset
-      // the 'partial full' flag.
-      partialFull_ = false;
+      VELOX_CHECK(
+          !partialFull_,
+          "Unexpected partial full when there is no new distincts");
     }
   }
 }