Fix possible NPE in ordered window aggregates with filter

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,8 @@ Change Log
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>PR #1660: Optimize window aggregates with AND UNBOUNDED FOLLOWING and no exclusions
+</li>
 <li>PR #1656: Optimize window aggregates with ORDER BY + UNBOUNDED PRECEDING + no exclusions
 </li>
 <li>Issue #1654: OOM in TestMemoryUsage, in big mode

h2/src/main/org/h2/expression/analysis/DataAnalysisOperation.java

@@ -345,7 +345,11 @@ public abstract class DataAnalysisOperation extends Expression {
             data = partition.getData();
         }
         if (forOrderBy || !isAggregate()) {
-            return getOrderedResult(session, groupData, partition, data);
+            Value result = getOrderedResult(session, groupData, partition, data);
+            if (result == null) {
+                return getAggregatedValue(session, null);
+            }
+            return result;
         }
         // Window aggregate without ORDER BY clause in window specification
         Value result = partition.getResult();

h2/src/test/org/h2/test/scripts/functions/aggregate/array-agg.sql

@@ -107,15 +107,18 @@ SELECT ARRAY_AGG(ID ORDER BY ID) OVER (PARTITION BY NAME), NAME FROM TEST;
 > [4, 5, 6]                                          c
 > rows: 6
 
-SELECT ARRAY_AGG(ID ORDER BY ID) FILTER (WHERE ID < 3 OR ID > 4) OVER (PARTITION BY NAME), NAME FROM TEST ORDER BY NAME;
-> ARRAY_AGG(ID ORDER BY ID) FILTER (WHERE ((ID < 3) OR (ID > 4))) OVER (PARTITION BY NAME) NAME
-> ---------------------------------------------------------------------------------------- ----
-> [1, 2]                                                                                   a
-> [1, 2]                                                                                   a
-> null                                                                                     b
-> [5, 6]                                                                                   c
-> [5, 6]                                                                                   c
-> [5, 6]                                                                                   c
+SELECT
+    ARRAY_AGG(ID ORDER BY ID) FILTER (WHERE ID < 3 OR ID > 4) OVER (PARTITION BY NAME) A,
+    ARRAY_AGG(ID ORDER BY ID) FILTER (WHERE ID < 3 OR ID > 4) OVER (PARTITION BY NAME ORDER BY ID) AO,
+    ID, NAME FROM TEST ORDER BY ID;
+> A      AO     ID NAME
+> ------ ------ -- ----
+> [1, 2] [1]    1  a
+> [1, 2] [1, 2] 2  a
+> null   null   3  b
+> [5, 6] null   4  c
+> [5, 6] [5]    5  c
+> [5, 6] [5, 6] 6  c
 > rows (ordered): 6
 
 SELECT ARRAY_AGG(SUM(ID)) OVER () FROM TEST;