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https://issues.apache.org/jira/browse/PIG-2009?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Olga Natkovich updated PIG-2009:
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Fix Version/s: (was: 0.10)
> Better MergeForEach rule
> ------------------------
>
> Key: PIG-2009
> URL: https://issues.apache.org/jira/browse/PIG-2009
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 0.9.0
> Reporter: Daniel Dai
> Assignee: Daniel Dai
>
> MergeForEach rule will not merge two consecutive ForEach if the second
> ForEach has inner relational plan. This prevent some optimizations. Eg,
> {code}
> A = LOAD 'input1' AS (a0, a1, a2);
> B = LOAD 'input2' AS (b0, b1, b2);
> C = cogroup A by a0, B by b0;
> D = foreach C { E = limit A 10; F = E.a1; G = DISTINCT F; generate group,
> COUNT(G);};
> explain D;
> {code}
> We add ForEach after cogroup to prune B, however, we cannot merge this
> ForEach with D. Secondary key optimization for this query is thus disabled.
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