[jira] [Created] (HIVE-8215) Multi-table insertion optimization #3: use 1+1 tasks instead of 1+N tasks [Spark Branch]

["Chao (JIRA)" <ji...@apache.org>]

Chao created HIVE-8215:
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             Summary: Multi-table insertion optimization #3: use 1+1 tasks instead of 1+N tasks [Spark Branch]
                 Key: HIVE-8215
                 URL: https://issues.apache.org/jira/browse/HIVE-8215
             Project: Hive
          Issue Type: Improvement
          Components: Spark
            Reporter: Chao


Currently, for multi-table insertion it generates 1+N tasks - "1" is the task that generates input, and "N" are the insert queries that read from the input and write to separate output tables.

In order to make these N tasks run in parallel, we rely on {{hive.exec.parallel}} to be set to {{true}}. In this patch, we propose an alternative approach, which is to combine these N tasks into one single task, which contains N separate operator trees, which in execution leads to N result RDDs. We then may be able to execute these N RDDs in parallel inside Spark, without needing {{hive.exec.parallel}}.



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