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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gunther Hagleitner updated PIG-627:
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Attachment: multiquery_0223.patch
This is for the multiquery branch. It's phase 1. It contains a lot of
infrastructural work to be able to look at entire scripts during evaluation
(batch mode). It will look at a script plan and insert splits whenever there is
a shared sequence of operations. The split execution is still the same as it
was before (load-store bridge).
> PERFORMANCE: multi-query optimization
> -------------------------------------
>
> Key: PIG-627
> URL: https://issues.apache.org/jira/browse/PIG-627
> Project: Pig
> Issue Type: Improvement
> Affects Versions: types_branch
> Reporter: Olga Natkovich
> Fix For: types_branch
>
> Attachments: multiquery_0223.patch
>
>
> Currently, if your Pig script contains multiple stores and some shared
> computation, Pig will execute several independent queries. For instance:
> A = load 'data' as (a, b, c);
> B = filter A by a > 5;
> store B into 'output1';
> C = group B by b;
> store C into 'output2';
> This script will result in map-only job that generated output1 followed by a
> map-reduce job that generated output2. As the resuld data is read, parsed and
> filetered twice which is unnecessary and costly.
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