Windowing processing may have run into Exceptions when the whole tabl…

…e was processed (#15064)

Earlier when the query was processing the whole table; the planning may have ended with a NPE; as it was not possible to create a scanquery from it.

sql/src/main/java/org/apache/druid/sql/calcite/rel/DruidQuery.java

@@ -1432,17 +1432,14 @@ private WindowOperatorQuery toWindowQuery()
     if (windowing == null) {
       return null;
     }
-
-    final DataSource myDataSource;
     if (dataSource instanceof TableDataSource) {
-      // In this case, we first plan a scan query to pull the results up for us before applying the window
-      myDataSource = new QueryDataSource(toScanQuery());
-    } else {
-      myDataSource = dataSource;
+      // We need a scan query to pull the results up for us before applying the window
+      // Returning null here to ensure that the planner generates that alternative
+      return null;
     }
 
     return new WindowOperatorQuery(
-        myDataSource,
+        dataSource,
         new LegacySegmentSpec(Intervals.ETERNITY),
         plannerContext.queryContextMap(),
         windowing.getSignature(),

sql/src/test/java/org/apache/druid/sql/calcite/CalciteWindowQueryTest.java

@@ -54,6 +54,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.assumeThat;
+import static org.junit.Assume.assumeTrue;
 
 /**
  * These tests are file-based, look in resources -> calcite/tests/window for the set of test specifications.
@@ -101,6 +102,7 @@ public CalciteWindowQueryTest(
   @SuppressWarnings("unchecked")
   public void windowQueryTest() throws IOException
   {
+    assumeTrue("These tests are only run in sqlCompatible mode!", NullHandling.sqlCompatible());
     final Function<String, String> stringManipulator;
     if (NullHandling.sqlCompatible()) {
       stringManipulator = s -> "".equals(s) ? null : s;

sql/src/test/resources/calcite/tests/window/no_grouping.sqlTest

@@ -0,0 +1,29 @@
+type: "operatorValidation"
+
+sql: |
+  SELECT
+    m1,
+    COUNT(m1) OVER () cc
+  FROM druid.foo
+
+expectedOperators:
+  - type: "naivePartition"
+    partitionColumns: []
+  - type: "window"
+    processor:
+      type: "framedAgg"
+      frame: { peerType: "ROWS", lowUnbounded: true, lowOffset: 0, uppUnbounded: true, uppOffset: 0 }
+      aggregations:
+        - type: "filtered"
+          aggregator: {"type":"count","name":"w0"}
+          filter:
+            type: not
+            field: {"type":"null","column":"m1"}
+          name: null
+expectedResults:
+  - [1.0,6]
+  - [2.0,6]
+  - [3.0,6]
+  - [4.0,6]
+  - [5.0,6]
+  - [6.0,6]