[jira] [Commented] (HIVE-11152) Swapping join inputs in ASTConverter

["Laljo John Pullokkaran (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-11152?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14609381#comment-14609381 ] 

Laljo John Pullokkaran commented on HIVE-11152:
-----------------------------------------------

[~jcamachorodriguez] 
1. 
Add a comment to plan modifier why are we adding project only if right is a join and left is not a join (about swapping left and right). This is little bit of a hack in the sense that swapping is done by ASTConverter.  Swapping should be done by PlanModifier instead as it is its purpose.
This should be done in a separate pass in planmodifier(or keep track of joins that need this swap).

2. With #1 changes in ASTConverter will be migrated to PlanModifier.


> Swapping join inputs in ASTConverter
> ------------------------------------
>
>                 Key: HIVE-11152
>                 URL: https://issues.apache.org/jira/browse/HIVE-11152
>             Project: Hive
>          Issue Type: Bug
>          Components: CBO
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-11152.patch
>
>
> We want that multijoin optimization in SemanticAnalyzer always kicks in when CBO is enabled (if possible). For that, we may need to swap the join inputs when we return from CBO through the Hive AST.



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