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https://issues.apache.org/jira/browse/PIG-1568?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xuefu Zhang updated PIG-1568:
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Attachment: jira-1568-1.patch
> 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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