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https://issues.apache.org/jira/browse/HIVE-15192?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vineet Garg updated HIVE-15192:
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    Attachment: HIVE-15192.9.patch

Addressed review comments

> Use Calcite to de-correlate and plan subqueries
> -----------------------------------------------
>
>                 Key: HIVE-15192
>                 URL: https://issues.apache.org/jira/browse/HIVE-15192
>             Project: Hive
>          Issue Type: Task
>          Components: Logical Optimizer
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>              Labels: sub-query
>         Attachments: HIVE-15192.2.patch, HIVE-15192.3.patch, 
> HIVE-15192.4.patch, HIVE-15192.5.patch, HIVE-15192.6.patch, 
> HIVE-15192.7.patch, HIVE-15192.8.patch, HIVE-15192.9.patch, HIVE-15192.patch
>
>
> HIVE currently tranform subqueries into SEMI-JOIN or LEFT OUTER JOIN. This 
> transformation occurs on query AST before generating logical plan. These 
> transformations are described at [Link to original spec | 
> https://issues.apache.org/jira/secure/attachment/12614003/SubQuerySpec.pdf]. 
> Such transformations aren't able to handle a lot of subqueries, as a result 
> HIVE imposes various restrictions on the type of queries it could handle e.g. 
> Hive disallows nested subqueries. All current restrictions are detailed in 
> above linked document.
> This patch is 1st phase of getting rid of these transformations and leverage 
> Calcite's functionality to plan such queries. 
> Next phases will be lifting restrictions one by one. 
> Note that this patch already lifts one restriction *Restriction.6.m* (The LHS 
> in a SubQuery must have all its Column References be qualified)
> Known issues with this patch are:
>  * Return path tests fails for various reasons and are currently disabled. We 
> plan to fix and re-enable this later.
>   * Semi-join optimization (HIVE-15227) is disabled by default as it doesn't 
> work with this patch. We plan to fix this and re-enable it by default.



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