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https://issues.apache.org/jira/browse/HIVE-784?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matthew Weaver updated HIVE-784:
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Release Note: Not ready for release
Status: Patch Available (was: In Progress)
Support subqueries for 'WHERE IN (<subquery>)', initial version.
This is an initial implementation, not ready for submission (details below).
Nevertheless I would welcome comments on the approach.
- ASTRewriter.inSubqueryToJoin(). Currently is called right after
parsing, but will probably have to move later for proper alias
generation.
- This early version hard-codes a generated alias "t2" for subquery. To
fix, with guarantee of unique alias, will require moving the rewrite
into SemanticAnalyzer.analyzeInternal() after getMetaData().
- Currently only handles a top-level occurrence of WHERE IN
(<subquery>). Any nested occurrences will fail.
> Support uncorrelated subqueries in the WHERE clause
> ---------------------------------------------------
>
> Key: HIVE-784
> URL: https://issues.apache.org/jira/browse/HIVE-784
> Project: Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Ning Zhang
> Assignee: Matthew Weaver
>
> Hive currently only support views in the FROM-clause, some Facebook use cases
> suggest that Hive should support subqueries such as those connected by
> IN/EXISTS in the WHERE-clause.
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