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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-953) Enable merge join in pig to work with loaders and store functions which can internally index sorted data
Date Wed, 07 Oct 2009 19:45:31 GMT

    [ https://issues.apache.org/jira/browse/PIG-953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12763218#action_12763218
] 

Ashutosh Chauhan commented on PIG-953:
--------------------------------------

Changes look good. One comment I have:

1) In SortInfo.java#equals
We have two lists and we want to check for their equality. I quickly looked up jdk sources
and it seems that ArrayList doesn't override equals, so doing equals check on lists would
result in reference equality test which would be incorrect. Correct way to do this would be
to first check the sizes of two lists, if they are equal iterate through both lists and check
equality of items at the same index in two list.  

Few nits:
1) TestMergeJoin contains a System.err.println which we can get rid of.
2) There are few unused imports in patch.
3) SortInfo.java#getSortColInfoList may result in Findbugs warning because of similar reason
we discussed earlier in this jira. 

> Enable merge join in pig to work with loaders and store functions which can internally
index sorted data 
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: PIG-953
>                 URL: https://issues.apache.org/jira/browse/PIG-953
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: 0.3.0
>            Reporter: Pradeep Kamath
>            Assignee: Pradeep Kamath
>         Attachments: PIG-953-2.patch, PIG-953-3.patch, PIG-953.patch
>
>
> Currently merge join implementation in pig includes construction of an index on sorted
data and use of that index to seek into the "right input" to efficiently perform the join
operation. Some loaders (notably the zebra loader) internally implement an index on sorted
data and can perform this seek efficiently using their index. So the use of the index needs
to be abstracted in such a way that when the loader supports indexing, pig uses it (indirectly
through the loader) and does not construct an index. 

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