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From "Pradeep Kamath (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-845) PERFORMANCE: Merge Join
Date Thu, 13 Aug 2009 18:15:14 GMT

    [ https://issues.apache.org/jira/browse/PIG-845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12742914#action_12742914
] 

Pradeep Kamath commented on PIG-845:
------------------------------------

A couple of comments on new patch:
In MRCompiler.java, earlier there was code:

{code}
if(rightMROpr == null || rightMROpr.equals(curMROp))
 throw new MRCompilerException("Successor of right input not ...
{code}


{code}
if(curMROp.equals(rightMROpr)){
 int errCode = 2170;...
{code}

Do you also need to check rightMROpr == null here?

If index is empty it could mean one of the following two things:
1) Data for right input only has null for join key(s)
2) right input is empty
Are there any other reasons why the index would be empty?
In both these cases, join output would be empty - currently the code throws an exception
Should this change?
A unit test where right side input is empty would be a good one to add.






> PERFORMANCE: Merge Join
> -----------------------
>
>                 Key: PIG-845
>                 URL: https://issues.apache.org/jira/browse/PIG-845
>             Project: Pig
>          Issue Type: Improvement
>            Reporter: Olga Natkovich
>            Assignee: Ashutosh Chauhan
>         Attachments: merge-join.patch
>
>
> Thsi join would work if the data for both tables is sorted on the join key.

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