Pradeep Kamath created HIVE-3733:
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Summary: Improve Hive's logic for conditional merge
Key: HIVE-3733
URL: https://issues.apache.org/jira/browse/HIVE-3733
Project: Hive
Issue Type: Improvement
Reporter: Pradeep Kamath
If the config hive.merge.mapfiles is set to true and hive.merge.mapredfiles is
set to false then when hive encounters a FileSinkOperator when generating map
reduce tasks, it will look at the entire job to see if it has a reducer, if it
does it will not merge. Instead it should be check if the FileSinkOperator is a
child of the reducer. This means that outputs generated in the mapper will be
merged, and outputs generated in the reducer will not be, the intended effect
of setting those configs.
Simple repro:
set hive.merge.mapfiles=true;
set hive.merge.mapredfiles=false;
EXPLAIN
FROM <input_table>
INSERT OVERWRITE TABLE <output_table1> SELECT key, COUNT(*) group by key
INSERT OVERWRITE TABLE <output_table2> SELECT *;
The output should contain a Conditional Operator, Mapred Stages, and Move tasks
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