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https://issues.apache.org/jira/browse/HIVE-15539?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jesus Camacho Rodriguez updated HIVE-15539:
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Attachment: (was: HIVE-15539.patch)
> Optimize complex multi-insert queries in Calcite
> ------------------------------------------------
>
> Key: HIVE-15539
> URL: https://issues.apache.org/jira/browse/HIVE-15539
> Project: Hive
> Issue Type: Improvement
> Components: Parser
> Affects Versions: 2.2.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Attachments: HIVE-15539.01.patch
>
>
> Currently multi-insert queries are not optimized by Calcite. Proper
> integration with Calcite would include creating a _spool_ operator whose
> output is reused by every _insert_ statement; however, _spool_ operator has
> not been added to Calcite yet (CALCITE-481).
> In the meantime, and since complex logic for multi-insert queries is in FROM
> clause, we can optimize the FROM clause with Calcite and connect the
> optimized result to the original query.
> Initially, we will recognize three different cases:
> - FROM clause is trivial, e.g., table reference, or not supported. No need to
> optimize with Calcite.
> - FROM clause is a subquery. Optimize the subquery with Calcite.
> - FROM clause is a join. Rewrite join into a subquery and optimize it with
> Calcite. Change references in INSERT statements to refer to subquery columns.
> This should be beneficial for MERGE statements processing too, since MERGE
> statements are treated as multi-insert queries by Hive.
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