[jira] [Created] (DRILL-1946) Wrong result for aggregation query with lower slice_target

[Aman Sinha (JIRA)]

Aman Sinha created DRILL-1946:
---------------------------------

             Summary: Wrong result for aggregation query with lower slice_target
                 Key: DRILL-1946
                 URL: https://issues.apache.org/jira/browse/DRILL-1946
             Project: Apache Drill
          Issue Type: Bug
          Components: Execution - Operators
    Affects Versions: 0.7.0
            Reporter: Aman Sinha
            Assignee: Chris Westin


Here's the result with the default value of slice_target for the following 
query: 
{code}
select count(*) from (
SELECT l_suppkey, sum(l_extendedprice)/sum(l_quantity)
FROM cp.`tpch/lineitem.parquet`
WHERE (l_orderkey in (SELECT o_orderkey FROM cp.`tpch/orders.parquet`
                       WHERE o_custkey < 2) )
GROUP BY l_suppkey
);

+------------+
|   EXPR$0   |
+------------+
| 29         |
+------------+
{code}

I lowered the slice_target in order to force exchanges in the following query.  
The result is wrong.   
{code}
0: jdbc:drill:zk=local> alter session set `planner.slice_target` = 1;
select count(*) from (
SELECT l_suppkey, sum(l_extendedprice)/sum(l_quantity)
FROM cp.`tpch/lineitem.parquet`
WHERE (l_orderkey in (SELECT o_orderkey FROM cp.`tpch/orders.parquet`
                       WHERE o_custkey < 2) )
GROUP BY l_suppkey
);
+------------+
|   EXPR$0   |
+------------+
| 14         |
+------------+
{code}

The Explain plan for the second query has multiphase aggregates.  When I set 
planner.enable_multiphase_agg = false, the result is correct, so it seems to be 
a multiphase aggregate issue based on a preliminary analysis (although there 
might be other things going on). 



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