[CALCITE-6557] AggregateMergeRule throws 'type mismatch' AssertionError

The fix was to use the type of the upper aggregate call, rather than
the lower.

Author: julianhyde

core/src/main/java/org/apache/calcite/sql/SqlSplittableAggFunction.java

@@ -304,7 +304,7 @@ abstract class AbstractSumSplitter implements SqlSplittableAggFunction {
             bottom.isDistinct(), bottom.isApproximate(), false,
             bottom.rexList, bottom.getArgList(), bottom.filterArg,
             bottom.distinctKeys, bottom.getCollation(),
-            bottom.getType(), top.getName());
+            top.getType(), top.getName());
       } else {
         return null;
       }

core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java

@@ -6545,6 +6545,25 @@ private HepProgram getTransitiveProgram() {
         .check();
   }
 
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6557">[CALCITE-6557]
+   * AggregateMergeRule throws 'type mismatch' AssertionError</a>. The scenario
+   * has the same aggregate function (SUM) at multiple levels; the lower level
+   * is NOT NULL (because of GROUP BY) and the upper level is nullable. */
+  @Test void testAggregateMerge9() {
+    final String sql = "SELECT sum(deptno)\n"
+        + "FROM (\n"
+        + "    SELECT sum(deptno) AS deptno\n"
+        + "    FROM dept\n"
+        + "    GROUP BY name)";
+    sql(sql)
+        .withPreRule(CoreRules.AGGREGATE_PROJECT_MERGE,
+            CoreRules.PROJECT_MERGE)
+        .withRule(CoreRules.AGGREGATE_PROJECT_MERGE,
+            CoreRules.AGGREGATE_MERGE)
+        .check();
+  }
+
   /**
    * Test case for AggregateRemoveRule, should remove aggregates since
    * empno is unique and all aggregate functions are splittable.

core/src/test/resources/org/apache/calcite/test/RelOptRulesTest.xml

@@ -756,6 +756,28 @@ LogicalAggregate(group=[{}], X=[SUM($0)], Z=[MIN($1)])
       <![CDATA[
 LogicalAggregate(group=[{}], X=[SUM($5)], Z=[MIN($5)])
   LogicalTableScan(table=[[CATALOG, SALES, EMP]])
+]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testAggregateMerge9">
+    <Resource name="sql">
+      <![CDATA[SELECT sum(deptno)
+FROM (
+    SELECT sum(deptno) AS deptno
+    FROM dept
+    GROUP BY name)]]>
+    </Resource>
+    <Resource name="planBefore">
+      <![CDATA[
+LogicalAggregate(group=[{}], EXPR$0=[SUM($1)])
+  LogicalAggregate(group=[{1}], DEPTNO=[SUM($0)])
+    LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
+]]>
+    </Resource>
+    <Resource name="planAfter">
+      <![CDATA[
+LogicalAggregate(group=[{}], EXPR$0=[SUM($0)])
+  LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
 ]]>
     </Resource>
   </TestCase>

core/src/test/resources/sql/agg.iq

@@ -147,6 +147,24 @@ from (select deptno, count(*) from emp group by deptno);
 
 !ok
 
+# [CALCITE-6557] AggregateMergeRule throws 'type mismatch' AssertionError
+#
+# The scenario has the same aggregate function (SUM) at multiple levels; the
+# lower level is NOT NULL (because of GROUP BY) and the upper level is nullable.
+SELECT sum(deptno) AS s
+FROM (
+    SELECT sum(deptno) AS deptno
+    FROM dept
+    GROUP BY dname);
++-----+
+| S   |
++-----+
+| 100 |
++-----+
+(1 row)
+
+!ok
+
 # [CALCITE-998] Exception when calling STDDEV_SAMP, STDDEV_POP
 # stddev_samp
 select stddev_samp(deptno) as s from emp;
@@ -3778,4 +3796,5 @@ select distinct sum(deptno + '1') as deptsum from dept order by 1;
 (1 row)
 
 !ok
+
 # End agg.iq