Xuefu Zhang created HIVE-8118:
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Summary: SparkMapRecorderHandler and SparkReduceRecordHandler
should be initialized with multiple result collectors[Spark Branch]
Key: HIVE-8118
URL: https://issues.apache.org/jira/browse/HIVE-8118
Project: Hive
Issue Type: Bug
Components: Spark
Reporter: Xuefu Zhang
In the current implementation, both SparkMapRecordHandler and
SparkReduceRecorderHandler takes only one result collector, which limits that
the corresponding map or reduce task can have only one child. It's very comment
in multi-insert queries where a map/reduce task has more than one children. A
query like the following has two map tasks as parents:
{code}
select name, sum(value) from dec group by name union all select name, value
from dec order by name
{code}
It's possible in the future an optimation may be implemented so that a map work
is followed by two reduce works and then connected to a union work.
Thus, we should accommodate this. Tez is currently providing a collector for
each child operator in the map-side or reduce side operator tree.
Likely this is a big change. With this, we can have a simpler and clean
multi-insert implementation.
This is also the problem observed in HIVE-7731.
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