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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-1568) Optimization rule FilterAboveForeach is too restrictive and doesn't handle project * correctly
Date Thu, 26 Aug 2010 17:39:54 GMT

     [ https://issues.apache.org/jira/browse/PIG-1568?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Xuefu Zhang updated PIG-1568:
-----------------------------

    Status: Open  (was: Patch Available)

> Optimization rule FilterAboveForeach is too restrictive and doesn't handle project *
correctly
> ----------------------------------------------------------------------------------------------
>
>                 Key: PIG-1568
>                 URL: https://issues.apache.org/jira/browse/PIG-1568
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Xuefu Zhang
>            Assignee: Xuefu Zhang
>             Fix For: 0.8.0
>
>         Attachments: jira-1568-1.patch, jira-1568-1.patch
>
>
> FilterAboveForeach rule is to optimize the plan by pushing up filter above previous foreach
operator. However, during code review, two major problems were found:
> 1. Current implementation assumes that if no projection is found in the filter condition
then all columns from foreach are projected. This issue prevents the following optimization:
>     	A = LOAD 'file.txt' AS (a(u,v), b, c);
>     	B = FOREACH A GENERATE $0, b;
>     	C = FILTER B BY 8 > 5;
>     	STORE C INTO 'empty';
> 2. Current implementation doesn't handle * probjection, which means project all columns.
As a result, it wasn't able to optimize the following:
>     	A = LOAD 'file.txt' AS (a(u,v), b, c);
>     	B = FOREACH A GENERATE $0, b;
>     	C = FILTER B BY Identity.class.getName(*) > 5;
>     	STORE C INTO 'empty';

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