[jira] [Created] (CALCITE-6087) EnumerableSortedAggregate returns incorrect result when input is empty

[Ruben Q L (Jira)]

Ruben Q L created CALCITE-6087:
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             Summary: EnumerableSortedAggregate returns incorrect result when 
input is empty
                 Key: CALCITE-6087
                 URL: https://issues.apache.org/jira/browse/CALCITE-6087
             Project: Calcite
          Issue Type: Bug
          Components: core
    Affects Versions: 1.35.0
            Reporter: Ruben Q L


Performing a MAX on an empty table (or on a table where we apply a filter which 
does not return any value) shall return NULL, we can verify this with our 
"standard" {{EnumerableAggregate}} operator:
{code:java}
  @Test void enumerableAggregateOnEmptyInput() {
    tester(false, new HrSchema())
        .query("select max(deptno) as m from emps where deptno>100")
        .explainContains(
            "EnumerableAggregate(group=[{}], m=[MAX($1)])\n"
            + "  EnumerableCalc(expr#0..4=[{inputs}], expr#5=[100], 
expr#6=[>($t1, $t5)], proj#0..4=[{exprs}], $condition=[$t6])\n"
            + "    EnumerableTableScan(table=[[s, emps]])")
        .returnsOrdered("m=null");
  }
{code}
However, if we use {{Hook.PLANNER}} to force the aggregation to be implemented 
via {{EnumerableSortedAggregate}} on the same query:
{code:java}
  @Test void enumerableSortedAggregateOnEmptyInput() {
    tester(false, new HrSchema())
        .query("select max(deptno) as m from emps where deptno>100")
        .withHook(Hook.PLANNER, (Consumer<RelOptPlanner>) planner -> {
          planner.removeRule(EnumerableRules.ENUMERABLE_AGGREGATE_RULE);
          planner.addRule(EnumerableRules.ENUMERABLE_SORTED_AGGREGATE_RULE);
        })
        .explainContains(
            "EnumerableSortedAggregate(group=[{}], m=[MAX($1)])\n"
            + "  EnumerableCalc(expr#0..4=[{inputs}], expr#5=[100], 
expr#6=[>($t1, $t5)], proj#0..4=[{exprs}], $condition=[$t6])\n"
            + "    EnumerableTableScan(table=[[s, emps]])")
        .returnsOrdered("m=null");
  }
{code}
It fails, because the EnumerableSortedAggregate returns an empty result set 
rather than NULL:
{noformat}
java.lang.AssertionError: 
Expected: "m=null"
     but: was ""
{noformat}



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