Steve Carlin created IMPALA-13587:
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Summary: Calcite planner: outer join not aggregating nulls properly
Key: IMPALA-13587
URL: https://issues.apache.org/jira/browse/IMPALA-13587
Project: IMPALA
Issue Type: Sub-task
Reporter: Steve Carlin
The following query is producing incorrect results:
select t2.int_col y from alltypessmall t1 left outer join alltypestiny t2 on
t1.int_col = t2.int_col group by 1
... due to nulls not being aggregated properly on multiple nodes. This is
because the value equivalency graph is being set for the join conjunct on an
outer join. When a hash join partition node is being used, there is an
optimization that skips the aggregation step that combines groups across nodes
if, based on the value transfer graph, it deduces that all data for the
partition column is being sent to the same node.
The bug here is that even though an outer join is using an equi-conjunct, the
left and right side are different when data is not found on the outer join
side, where it becomse null.
The fix is to avoid registering the equi-conjunct if the values are not always
equal.
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