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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12679797#action_12679797
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rding edited comment on PIG-627 at 3/6/09 5:59 PM:
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This patch contains the enhanced split operator to support multi-store queries.
It instroduces a new MROperPlan adjuster that merges single-load mapper-only
MapReduceOper to its predecesor based on the (implicit) split boundary. The
goal is to reduce the total number of MR jobs for a given multi-query task.
This patch is for the multi query branch
was (Author: rding):
This patch contains the enhanced split operator to support multi-store
queries. It instroduces a new MROperPlan adjuster that merges single-load
mapper-only MapReduceOper to its predecesor based on the (implicit) split
boundary. The goal is to reduce the total number of MR jobs for a given
multi-query task.
> 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: file_cmds-0305.patch, multi-store-0303.patch,
> multi-store-0304.patch, multiquery_0223.patch, multiquery_0224.patch,
> multiquery_0306.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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