Fix checked BIGINT SUM CI expectations

Signed-off-by: Kai Huang <ahkcs@amazon.com>

Author: ahkcs

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalcitePPLAggregationIT.java

@@ -196,10 +196,10 @@ public void testSumAvgLongOverflow() throws IOException {
     // Metric ordering remains in Calcite because OpenSearch exposes metric sort values as doubles,
     // which cannot distinguish these sums. Lexical tie-breaking would otherwise put "a" first.
     JSONObject exactSort =
-        executeQuery(String.format("source=%s | stats sum(v) as s by g | sort - s", exactSortIndex));
+        executeQuery(
+            String.format("source=%s | stats sum(v) as s by g | sort - s", exactSortIndex));
     verifySchema(exactSort, schema("s", "bigint"), schema("g", "string"));
-    verifyDataRows(
-        exactSort, rows(4611686018427387905L, "z"), rows(4611686018427387904L, "a"));
+    verifyDataRows(exactSort, rows(4611686018427387905L, "z"), rows(4611686018427387904L, "a"));
   }
 
   @Test

integ-test/src/test/java/org/opensearch/sql/ppl/StatsCommandIT.java

@@ -512,13 +512,7 @@ public void testSumWithNull() throws IOException {
                 "source=%s | where age = 36 | stats sum(balance)",
                 TEST_INDEX_BANK_WITH_NULL_VALUES));
     verifySchema(response, schema("sum(balance)", null, "bigint"));
-    // TODO: Fix -- temporary workaround for the pushdown issue:
-    //  The current pushdown implementation will return 0 for sum when getting null values as input.
-    //  Returning null should be the expected behavior.
-    // The analytics-engine backend (DataFusion) follows the SQL spec like Calcite-no-pushdown —
-    // SUM of all-null is null, not 0.
-    Integer expectedValue = (isPushdownDisabled() || isAnalyticsParquetIndicesEnabled()) ? null : 0;
-    verifyDataRows(response, rows(expectedValue));
+    verifyDataRows(response, rows((Object) null));
   }
 
   @Test