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https://issues.apache.org/jira/browse/PIG-1321?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Olga Natkovich updated PIG-1321:
--------------------------------
Release Note:
This rule allows to merge togther two foreach statements if the following
preconditions are met:
- foreach statements are consecutive
- the second foreach is not nested
- the first foreach statement does not contain flatten
Example:
(1) Original code:
A = load 'file.txt' as (a, b, c);
B = foreach A generate a+b as u, c-b as v;
C = foreach B generate $0+5, v;
.....
(2) Optimized code:
A = load 'file.txt' as (a, b, c);
C = foreach A generate a+b+5, c-b;
......
> Logical Optimizer: Merge cascading foreach
> ------------------------------------------
>
> Key: PIG-1321
> URL: https://issues.apache.org/jira/browse/PIG-1321
> Project: Pig
> Issue Type: Sub-task
> Components: impl
> Affects Versions: 0.7.0
> Reporter: Daniel Dai
> Assignee: Xuefu Zhang
> Fix For: 0.8.0
>
> Attachments: pig-1321.patch
>
>
> We can merge consecutive foreach statement.
> Eg:
> b = foreach a generate a0#'key1' as b0, a0#'key2' as b1, a1;
> c = foreach b generate b0#'kk1', b0#'kk2', b1, a1;
> => c = foreach a generate a0#'key1'#'kk1', a0#'key1'#'kk2', a0#'key2', a1;
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