[ https://issues.apache.org/jira/browse/PIG-1324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13162404#comment-13162404 ] 

Jie Li commented on PIG-1324:
-----------------------------

What would be the difficulty to solve this issue?
                
> Logical Optimizer: Nested column pruning
> ----------------------------------------
>
>                 Key: PIG-1324
>                 URL: https://issues.apache.org/jira/browse/PIG-1324
>             Project: Pig
>          Issue Type: Sub-task
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Daniel Dai
>            Assignee: Daniel Dai
>
> Currently, column pruning does not prune sub-fields inside a complex data-type. For example:
> A = load '1.txt' as (a0, a1, a2);
> B = group A by a0;
> C = foreach B generate group, SUM(A.a1);
> Currently, since we group A as a bag, and some part of the bag is used in the following statement, so none of the fields inside A can be pruned. We shall keep track of sub-fields and figure out a2 is not actually needed.

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