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https://issues.apache.org/jira/browse/PIG-922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12747521#action_12747521
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Santhosh Srinivasan commented on PIG-922:
-----------------------------------------
I am not sure about the logic for handling cogroup. Let me take another example
of an operator with multiple inputs - union. If you look at the code below, the
method returns a single required fields element. The required fields element
contains a reference to all the inputs that are required to compute that
particular column. However, wrt cogroup you are returning a list of required
fields that contains nulls for all the positions that are of no interest.
{code}
+ ArrayList<Pair<Integer, Integer>> inputList = new
ArrayList<Pair<Integer, Integer>>();
+ for (int i=0;i<predecessors.size();i++)
+ inputList.add(new Pair<Integer, Integer>(i, column));
+ List<RequiredFields> result = new ArrayList<RequiredFields>();
+ result.add(new RequiredFields(inputList));
+ return result;
{code}
> Logical optimizer: push up project
> ----------------------------------
>
> Key: PIG-922
> URL: https://issues.apache.org/jira/browse/PIG-922
> Project: Pig
> Issue Type: New Feature
> Components: impl
> Affects Versions: 0.3.0
> Reporter: Daniel Dai
> Assignee: Daniel Dai
> Fix For: 0.4.0
>
> Attachments: PIG-922-p1_0.patch, PIG-922-p1_1.patch,
> PIG-922-p1_2.patch
>
>
> This is a continuation work of
> [PIG-697|https://issues.apache.org/jira/browse/PIG-697]. We need to add
> another rule to the logical optimizer: Push up project, ie, prune columns as
> early as possible.
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