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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12681897#action_12681897
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Richard Ding edited comment on PIG-627 at 3/13/09 2:18 PM:
-----------------------------------------------------------
This patch completes the phase 2 development as sepecified in the document
http://wiki.apache.org/pig/PigMultiQueryPerformanceSpecification:
# Allow multiple stores in single job
# Merge multiple plans into the split operator
# Terminate all but one with stores
As an example, the Pig script
{code}
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';
{code}
in the introduction of this bug now results in a single map-reduce job.
This patch is for the multi query branch.
was (Author: rding):
This patch completes the phase 2 development as sepecified in the document
http://wiki.apache.org/pig/PigMultiQueryPerformanceSpecification:
# Allow multiple stores in single job
# Merge multiple plans into the split operator
# Terminate all but one with stores
This patch is for the multi query branch.
> PERFORMANCE: multi-query optimization
> -------------------------------------
>
> Key: PIG-627
> URL: https://issues.apache.org/jira/browse/PIG-627
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 1.0.0
> Reporter: Olga Natkovich
> Attachments: file_cmds-0305.patch, multi-store-0303.patch,
> multi-store-0304.patch, multiquery-phase2_0313.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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